No Internet?          
           I can not get connected to the web ?  Assumptions !

Warning 1 for virus magnet XP Windows, XP does not run WIFI  WPA2 ! mode until SP2 or SP3 is installed +Wanacry. (SP3 is the best answer here for vast reasons) Service Pack3. (and this warning)
Looks like Microsoft deleted the SP3 , so get it here.

First off  if you connect any PC to the router wired with a Ethernet CABLE and if that works then internet is not dead is it? no it is not. (cat 5/6 cables are cheap own at least one)
If  Ethernet  works, and only 1 WIFI PC or Cell phone fails on WIFI the that device be it PC or CELL has wifi problems.
I will not cover 3/4/5G service called wireless , at all  so do call your 3G service provider and get help (Verizon or T-Mobile or what ever you have for this service provider)
If Ethernet wired fails on only 1 PC then load the missing driver for that Ethernet port (device) per this way.
If Ethernet works and only wifi fails, then read the below sections as they apply.

To use wifi you need your login credentials or use WPS magic login. (if your router support this method) RTM read your routers manual to use that. (WPS = wifi protected setup , magic)
There are only 2 ways to learn your credentials, (you are the owner of your router, and know them, are not, the ISP owns it and told you them on install day or hand you a card with said credentials.
SSID is your WIFi broadcast name.
EG: SSID = Ghost1a  , encryption set to = WPA/WPA2-Personal  and last your very own Pass-Phrase (word) like this : 1@357azB!uyk (use your own code)
A good password makes the wifi very secure.

See my short wifi security section.
There are vast ways to lose the internet . (both hardware or software caused or not configured correctly, or you ISP is off line now or today or ? Call them?))
The best way to test is to  have 2 good PC's and test them both on your Router, do both fail?  (yes, borrow a PC or ask a friend to test your router for up or down status)

ETHERNET is the best , fastest and the most easy to setup) In the world of high tech, always try simple first, then play wifi last, or never.
In fact your PC came new, out of the box (OOBE) with a working Ethernet ready to work, if you just plugged into the router or modem directly it will work, 99% of the time)
Sadly the new thin flimsy PCs (notepads have no Ethernet JACK) and are a huge pain to test or setup. (not me, I have special tools)
I will never attempt to cover 36 years of  PC connections, only the most common and most problematic older PCs. (like 5 to 15 years old)
Here are some common network connections, at home.
If you run old LAN  cards, NICs of any kind, like relic 10 or 100 base  not far better  1000Mb/s  speeds,  nothing beats (at home no fiber) 1000Mbit/s Ethernet, but Modern WiFI can beat the old 10/100Mbit/s NIC cards and chips made long ago.
If you have an older or relic slow router running 10/100 speeds your internet will be slow.(as will Wifi).
Next is your ISP modem , of many types some are slow others are fast or super fast,and you get exactly what you pay for in service, avoid dial up  and DLS, best is FIOS (glass fiber FC)  to the home and next is 16 channel cable modems.

 (wired is super easy , called Ethernet)
 Just plug it and and it will work ! If not call the ISP or read the below details.

Let say the cable modem is wired to the ISP cable and the modem jack on the rear (Ethernet) is wired to M (for modem) jack below and Power P wire is connected to power pack and has power to the wall AC.
I will assume you have a router (it be wise to have it) and it has  bank of Ethernet ports and WIFI antenna's. (here is mine)
Just connect these parts, up with CAT5/6 cable, (Walmart sells the cable at  the rack left at photo counter left) buy one, say 15ft. (5meters){100meters max}
See E port below is Ethernet port 1 to 4 all work pick one, , connect your PC to say port 1,  and the other end of this CAT:5/6 cable say 15  foot long. 
This Cable wired goes to your PC matching type RJ45 Jack
It is the same kind of  RJ45 jack called LAN or Ethernet. (do not use old landlines phone cables, that look kinda like this but has only 4 pins)
P =  power, the router must  have power from the power pack to the wall AC jack (the LED glows on the router)
M= Modem goes to your modem if your ISP gave you only one box, it maybe a 2 in 1 box,  Modem + rotor or even 3 things with WIFI. (in that case there is no M jack only a CABLE JACK to the TV cable system or to DSL)
Let me stop here and say your ISP responsibility ends at the E JACK, the make it work there at E and your responsibility is find a good PC that works there.
True to is if the ISP sold you WIFI then they help you get that working, so call them.
You turn on your PC and this E cable below starts working by the magic of Windows, (or Linux) (plug and play (PnP)does that)
We always do this first so we can do fast MS updates or get huge video drivers or just use it all the time , it is the fastest connection of all , this one here is  a GigaLan speed port. I use it all the time, at home.
Wifi is slow and problematic for may locations in the USA. We use WIFI here only to lower our CELL phone data bills, to zero. (wifi turned on, at home)
All our TVs are Ethernet wired to here.

Typical Examples of connections shown here:
The Router on the left DIR-655,  and the Desktop PC on the right (relic) has on board Ethernet chip, (good Laptop PCs have the same RJ45 Ethernet jack there.)
Photos: (the plug has a spring plastic lock, do not force it out, depress the TAB first)
THIS blue cable goes to E on the left.
This is a very common PCI Ethernet card, used on very very old Desktops,  The best ones are GigaLan rated and PCIe slots. The below right photo is an very modern top class (love them) Asus M5a99FX MOBO;
this is the E jack , Ethernet with 8pins Gold.
Photo of CAT5 RJ45 Ethernet connectors must before the crimp actions.(this is an advanced type of connector making the fit up more easy) Call this the E cable.
I am making my own cable now with my special tools. Most folks just buy a cable. But  home made are vastly cheaper, 10 cent connectors.

What if Ethernet fails.? It should not, but can. (running XP or VISTA  both are now a dead OS)  
On top reason for the Ethernet dead, on old dead now  XP is the missing old old Realtek chip 8101L driver. (how it got dead?, is easy, after 16 years someone deleted it, for SURE)
Realtek (but  never Intel) web site is a horror to navigate, now, with missing links and dead links. The above driver is here and is official 8101L , 8130,8139 (click Global !)
The XP plug  and play driver servers are now down read my drivers page now, so  expect problems with XP. (Vista now too, spring 2017 are now zero support)
How to find drivers on old non supported PCs is and ART , A SKILL set. What I do is learn what chip is dead, what is its makers name and true model number , in all cases (PnP failures)

As soon as I see my , E port dead, I do this:
I click Control Panel  in the start button, then pick device manager (DM) and then find this page below, photo3. (in the run box type devmgmt.msc)
See the DM photo below.
See "network adapters"  bingo.
Below is a LAN wired chip 82577  and below it is WLAN wireless chip wireless. N6200, your PC has different chip names, but are very important to know if DEAD !
See my Gigalan chip from intel (or yours might be Realtek or other brands Broadcom?)
Double left click it that line, first see "device is working" then if it's not working click  update Driver software..  (right clicked)
 If the Ethernet is dead, you can't  update Dead via the dead port because of,,, the,,,,
(The classic Chicken and the EGG conundrum.)
If this happens to you? , (mostly on old XP  and VISTA) we find any working web connected PC anywhere on earth and download the correct matching driver (the OS, and CHIP there must match)

If your PC has no local driver for your E chip, it fails,  I then go to and get the  correct LAN driver,  for you exact PC and matched to your exact OS version.
If the Ethernet is working you can click on the wireless chip below and do an update, in all cases W7 and UP.  XP is dead now. (like a barrel of rotting apples XP is)
Photo:3: W10 DM.  If  a line is RED/YELLOW or Unknown, that means the Driver is BAD ! (missing in most cases) In all cases it means PnP could not find the correct driver, for these reasons.
The 577 is my E chip, the next chip is wifi  in my case it is Centrino from intel.
Getting the above ETHERNET to work first , makes getting wifi up 10 times more easy, now that the internet is working. (PnP will start working (not XP nor VAST now)
You found your chips real name, then got the correct matching driver and now it works.

If the PC is 10 years old or less find the driver at HP driver pages for your PC, 
The Task bar  Ethernet ICON will not have X marked across it, telling you the Ethernet is not dead here > no X mark in the E Icon means it's working.
If PnP fails to find the wifi chip then the process to find a good driver is the same. As shown here.

We enter here, at this point Ethernet works and the wireless driver in DM above is not dead.
To fix wifi in your PC, first make sure the driver is loaded. (and not missing or corrupted , best it to fresh load it now) as seen here.
We look to see if the WIFI card (or dongle) is not missing, too.
Next is the windows setup (W10)
  • Click control panel (in the start run box type control)
  • Click network &sharing center.
  • click Setup a new connection.
  • Click "manually connect to a wireless network(IF MISSING THAT MEANS THE WIFI DRIVER IS DEAD OR MISSING or the wifi card is missing in its slot or USB port as the case may be)
  • Bingo do this. The SSID here is FIDO2.  (a dogs name or whatever you want) Then WPA2 and last very important is the key (pass word) write it down  now. Check the 2 boxes.
We set this up after the Router is setup first. (if the router is setup then this is all you need here)
Learn that vast numbers of laptops and all desktops have no wifi card at all , it was an OPTION then so what we do is look for it , and if missing buy one.
A USB wifi dongle is $3.

Next up is how to set up your router or wifi access point the why you want. Using the above credentials.

WIFI (wireless LAN WLAN):
Step 2, WiFi... wireless. I will do this manually for best security, no wizards do I  trust for wifi ever.
Next is configuring the Router, wireless pages. (I assume it's your router no the ISP and you know its password)
  1. Read the manual on your , router, mine is DIR655,  I read the manual and it tells me my router page is here.  Most router new , you power up and the LAN  is running now and firewall is in full protection.
  2. Page 16 tells me IP address is my page address. ,so paste that into any browser I use FF v66 firefox. and land on the Routers home page, login.
  3. The user name is admin and  the password is blank (changed my PW day 1, to "something secret" and write it down, ok?)
  4. I click Setup, click wireless settings top left. click manual wireless setup (bottom of page)
  5. Bingo you are there.See below settings,  These are best .
  6. Set the side to your DOG name or whatever floats your boat.  FIDO2, Is one silly example. Do not use same names as others seen in your hood.
  7. Next I pick a channel not used in the hood most.  (least used) Ch6 is  good guess.
  8. Avoid WEP, totally use WPA1 or 2.and last pick a KEY (use words not in any dictionary, like 1$xy59!@z, use what you want but do write it down,for all home users and Cell phones.
  9. Save settings first then exit setup and at any cell phone you can now see FIDO2 and connect easy. and last you PC does the same. (FIDO2, WPA, Key) 1,2,3 you are in.
  10. On the PC make sure its not in airplane mode. (wifi off nor off in BIOS) then do the setups, in said PC. FIDO2, WPA, and key) bingo you are now connected via WIFI.
Photo 5 Dir-655,
This is my router,  yours will be functionally the same, but total different pretty screens and have it's own login rules. (and IP address)

I kept this as short and sweet as possible.  (I don't use WPS , read you router manual to set up wireless protected setup and PIN) I consider WPS to be non secure.
If all this works, now the Internet works 2 ways, now, wired and wireless.
Best is to know how to use both, so you can fix problems as they arise.

At your PC say Windows 10.
How to switch back and forth from Wifi and wired (Ethernet)? {even both at the same time works}
This way below works best after setting it up in control panel first seen here.
Steps below: Clicks.
  • On the task bar double click this tiny connection icon (as see here, double left click this red arrow icon and pick any network you own (means have sign in credentials to)
  • Way 2 is next,, Push start  menu  and pick "Settings" (in the windows key usage , menu  Settings is in the "S" section )
  •  Then in the new W10 Setting menu pick , "network & Internet"
  • Then see the below menu,  if  Wi-Fi is missing that means your wifi drivers are missing wrong or corrupted, the cure is obvious; reload them fresh from HP.
  • If HP did not make your Wi_Fi device, then get the driver from you maker, of said device, 100 of makers, so, only you know what you bought and installed.
  • If said device is a USB -WiFi dongle, you need to get USB working first then get the correct driver from the dongle maker.
  • See the left side here,  If I click Ethernet I can use that to connect to it. Below is my 2 WI-FI routers, daisy chained on my GigaLAN , FIDO1 and 2.
  • I am on Ethernet now, but if I was to click Fido1 and connect it would then be on Wi-Fi. If this way fails do it this way above in control panel.

The below  is showing I am connected to Ethernet now.

Why WIFI is so hard to use and keep working,  WIFI is a problem child, unlike Ethernet, wired.  See jamming  and interference , here.
Let me list them. WIFI can be super unreliable in a big city what vast persons sharing 10 channels and huge electrical noise in this region. (crazy RFI)
  1. Drivers bad. or using the wrong ones. tops the list, see above sections for the cure. (or the classic failure, you (or others) upgraded to Windows 10 and the wifi chip is dead, well join the club.
  2. You are too far from the Router antenna's   even 50 feet is too far and if using bricks or concrete walls and worst of all steel walls or REBAR concrete fitted walls will  block RF signals easy. See how here.
  3. Lots of neighbors use you channels,  so use a different  radio band/channels , move higher see photo 5 above?, Use this program to see them all, and then move to a quiet channel.
  4. Interference,  Radios inside many devices, can jam wifi and BlueTooth(tm) can be jammed,  called RFI , Radio Frequency Interference.   (see this list of offenders)
  5. One tactic that works well,  is to kill the power to all rooms in the house, but the one AC power  jack running your router/modem,  does wifi work now? BINGO.  RFI  is real.
  6. Not running dual band WIFI ! single band is a relic, upgrade now.  (and for sure MU-MIMO routers)
  7. Even street lights in the hood can in fact jam wifi,  the ones with choppers inside,  just like the LED desk lamps used in your rooms  and are very bad RFI emitters.
  8. Some florescent lamp fixtures, have some very nasty electronic  digital ballast device inside, (not the nice transformer kinds) and it's really this very noisy  chopper inside,  ditch them for CLASS B rated devices, FCC.
  9. Old relic baby monitors also Jam 2.4GHz radio band,  This band is super busy.  Avoid all 2.4GHZ , other devices in the home that are not wifi devices.
  10. Learn to that wifi is  a SHARED resource , and is in public shared  too.  Wifi uses collision rules, that if overloaded/over crowded ,this causes it to run VASTLY SLOW.
  11. Use  wired LAN connections, any time you can and avoid all this PAIN.  Use WiFi only as a last resort. (or  as backup communication's)
  12. One way to reduce your RFI noise is to buy home devices that have real FCC (USA) Class B certifications. (no lies from China saying ,so but are not) Even those cheap imported screw in florescent lamps make noise. (Class A)
(1)The word kill above means flip the circuit breakers to OFF,  I have my router and modem on a UPS and I can run laptop on battery power and test the wifi with all power to the home cut dead, testing for wifi noise.
or unplug all things in all rooms 1 by 1,. (all power cords unplugged from walls, all lamps in the room off, as a test only) (but no the router or modem and the PC under test)
Wifi can have a very limited range as low as 50 feet.  (or none through solid or worse REBAR failed concrete or bricks.)
We can also upgrade the router to one that puts out full 1watt wifi power. 10x more. (D-link Dir-879)
The real hard nut cases , you can't turn off the power to a neighbors home to find who is jamming your WIFI.
But you can change channels in your router if you own it. Sure can. See wifi radar below and jamming next.

Last and not least is the WIFI RADAR , I call it that,  the executable file is called  Inssider.exe (mine is the older free version v2, and is very good)
It does not see jamming (or RFI) say from a baby monitor or any other non wifi noise sources. (it sees only wifi data)
See jamming here.
We run this program (app) older versions are  free, goggle it.  (your wifi chip/card but be working and not in airplane mode)
This is you and your neighbors, wifi broadcasts. (the photo below is random found ., not mine)
The SSID is your WIFI name, from your router.
The place to be is here, on dead unused  channels; see why?, less traffic. In my hood , I'm on the upper band, 2.4GHz, the 5GHz band suffers poor range and for sure through walls. (but is good have 2 band wifi end to end)
If you run the program on any laptop and on battery power you can walk from your router and see the RF signals  drop (RSSI)eg -74 is weak,  as it drops data speeds slow and far enough the link disconnects.|
Trick 2 is use channels that are weak,  below the bottom of this list are the weak channels , and you can use them with great advantages. (you strong, they weak) WIFI is radio technology.
9 Access points seen. Using WEP is a bad idea in my opinion, it has been cracked/hacked. I keep my  router WEP mode, DISABLED . In city this page is HUGE, and and some channels OVERLOADED BIG TIME.
My router is set to wpa/wpa2, only, and with huge passphrase using no dictionary words at all. 
(Today I run Cisco RV320 router (zero wifi) a  powered, D-link DIR-879 wireless router set up as WiFi extended wired  Access Point AP.) Firmware version 1.07 works great,  this is located in center of home and serves our cell phones , offloading 3G
Those are base bands,  or to a HAM guy and RF Carrier bands 2.4GHz, is here. (and channels) USA channels only here.
If you have 2 routers or 1 and  a wifi AP access point set one on a different channel.  Avoid that left yellow channel all the folks use due to ignorance.
RSSI  is the signal strength, use this on your laptop and see how your signal drops as you move around your house. The higher the colored signal goes the stronger it is,  -20 is very strong.
dBm is Decibels , related to 1 milliwatt power , higher than -80 is best,
If use the above program set to 5GHz tab, and  you move around the home, you will see that this band hates walls even more than 2.4. (easy as pie to test this theory using the free program above)
The worse case WIFI is in  high rise building with 1000 of wifi devices.(all fighting for 1 channel you are on)

Security and WIFI danger.
Do not use WEP it is insecure. (WPA2 is best)
In the router turn off ACCESS POINT and Pin codes, (the button on the side of the router, WPS, is now dead )  Wifi protected setup OFF.
Never use WEP encryption.
Always have pass phrase to log in to WIFI with 8-10 characters and ever use dictionary words ever.
Get a good router or update it so the KRACK , exploit  is not  there. (keeping remote access off and WPS is fast way to avoid KRACK)
Turn off remote access management  in the router
Turn WAN PING off,  (do not let the web hackers Ping YOU ever!)
Guest zone off, and DMZ off.
Have no holes in your Routers Fire wall, unless you know how to do that safely.
Never use  a  simple modem directly, always have  are router firewall there and setup clean.
Always keep the firmware in your router fresh and the most current. (go to the makers web site, and read what is newest here, directly and do get the KRACK fix as soon as it comes out)
And worse of all, running a 100% OPEN AD HOC wifi with zero security and no passwords. (you be doomed)

Wifi Sucks swap gas?: (why?) , yes
The reasons are 3 fold caused.
1: Wifi is Radio technology and can  fail for interference from other radio sources on the same bands, (baby monitors , old wireless phones or other things that are malfunctioning)
2: You have too many neighbors and they all have tons of wifi devices, and toys and the channels are jammed. (wifi is shared radio channel resource)
3: User ignorance, of  not knowing what to do, or not learning to use channels that are not overloaded.

Most homes have only 2 bands to use, or less. (2.4 and 5GHz bands)
Most homes are not using spec.  Wifi, (802.11a/h/j/n/ac/ax) systems, end to end.
That fact is  the channels 5GHz.  may suck the most, as it gets weaker faster through walls and for sure brick or concrete walls. (and slows down) 2.4G works better. The program Inssider.exe shows that and proves that if you do the tests.
No lie, the  2 bands are best or more, slow is better than DEAD.
The most common complaint is Netflix is slow, (shows buffering) Why use Wifi at all here? But texting works great, well gee whiz, texting uses almost zero bandwidth.
The speed of wifi drops as you walk your PC farther from the router, so folks that are savvy have many AP (access points using  WIFI bridges and repeaters ) so that all zones are hot and fast, but most folks do not know how to set this up.
Wifi also fails if you neighborhood is really dense, with everyone is on the  same band or worse same channels. see Insidder.exe running above, in my photo.
Wifi channels are SHARED in the in your neighborhood, and gets worse every year, do to the vast expansion of "internet of things" more toys ,even silly wifi toys and refrigerators.
Wifi can be jammed with other non wifi devices, like baby monitors , kids toy cars, and the like (endless toys)  or old home land line , wireless phones.
Learn what internet of things means,  picture your neighbor has 5 web cams,  and wifi connected refrigerator, and even the oven, and 5 kids, with (7 with mom/dad) with cell phones on wifi and watching steaming video.
If  you find that shared channels are overloaded above, you can move to other channels , in your routers setup pages.(or wifi Access point) 
One way to get better wifi is to  buy and install wired WIFI expander access points, and put them all over the house, mine are wired off a hub switch radially.  Each with a unique SSID and same PW.
Wifi can be great if say in rural setting and all bands are clear and clean.  (the Marketers lie and use this as an  example for speed.)
Last ,if your wifi works great,  then use it and don't read why it loves to fail here..., this page is NOT for you .
One possible cure is a more powerful wifi router.(see why?) above link.
The only way to find and cure non PC caused jamming is to own a $500 spectrum analyzer seen below, (portable with antenna) to find who what and where the jammer located. (FYI)

This device is expensive but finds them all. (a spectrum analyzer shows all noise and jamming signals)
We use Wifi here in our home only for CELL phone backup from 3/5g , drops to wifi. 
We know better than to fuss with wifi.  (use Inssider to see what's going on, but does not see JAMMING from non wifi sources like the below does.)
Remember that Inssider only SEES WIFI signals, not jamming or noises nor alien devices illegally on this wifi channels. (but is free and works great mostly in all cases, lacking jamming) (jamming can be on purpose or by accident)

by turning off  AC power panel circuit breakers you find the offending room that is jamming wifi. (very impossible to force neighbors to do that) so is limited by that.
Things you have that can jam your Wifi or your neighbors jam you. (RFI = Radio Frequency Interference)
Toy remote controlled cars, toy air planes, copters and the like with RF radio controls.
Baby monitors or camera monitors using RF radios channels, near 2.4GHz.
All LED lamps and florescent lamps can have very badly designed power supply inside (choppers),  not   FCC part B certified or  the  no name makers lied. (as sold on fleabay) 
I have  desk LED lamp that could be named RFI NOISE JAMMER easy.
One HAM radio trick (learned) is to kill power in the home "@ dah Breakers", room by room (not the AP) and see if WIFI wakes up, if yes, the turn that room back on then unplug each thing in that room 1 by 1 ,even toys batteries removed)
Some computer monitors very (20yo)old CRT are noise makers too. ( or older than 2010) CCFL based LCD screens some are very RFI noisy.
Wireless speakers for the home TV. (mine uses 2.4GHZ) so turn it off  see if TV's wifi wakes up?
Old land line home wireless phones can jam wifi. (has hand set , and base station and remotes) unplug it.
And last your condo neighbor has 50 wifi devices in his home and all use channel one,  so get the hell off channel one.
Netflix fails, or stalls or shows buffering or acts oddly is wifi messing up. (don't use Wifi , but do use Ethernet wired and never see Buffering ever again.)
If you must use WIFI move the WIFI access point closer to the TV , even on top of the TV on shelf above there.

Last but not least, you don't like wired Ethernet, (why?)
Well then GET WIRELESS  3/4/5G. Say from Version. (T-Mobile, etc)
Using this. (random picked by me, From Verizon, gee ask your Cell Phone service provider for a USB 3G modem they sell and support)  end wifi /wireless blues.

You are at home.  , not sitting in say StarBucks™ drinking their burnt coffee bean juice nor at the Air port or at WORK.
You are using your own router or wifi access point at home and is not ISP rented nor ISP locked out buy your ISP (internet service provider)
You should know your WIFI Credentials, if not reset you router and set it up fresh and new.
You  were smart and first downloaded the PDF book on your router and have it  ready to read in your document folders.
You are close to the router say withing 50 feet, and no brick walls between you and the router, AP. (AP means wifi Access Point)
The channels are complex so read this.(world wide in scope)
I will not try to guess, who or what your ISP (internet service provider) is,  Dial-up,  DSL, SAT modem, cable modem with 1 to 16 channel cable,  FIOS or 3/4g wireless cards (WWLAN)(or USB wireless stick?)
There are at least 6 ways to get internet service.  (pick one use that)
I will assume you have THEIR (ISP)  modem sitting there, and it works,  your ISP's job is only that.  (make that work).
The best way is to call the ISP and first connect up with the wired Ethernet cable to your Router, jack or test this cable directly to you cable modem.  or  call the ISP for SERVICE now.
The Modem must have power and shows status that it is connected on its LED lights.(it has a manual to read, and covers that topic) If not clear or confused now, call the ISP (on the horn/cell)

Jargon, all technology is full of these tech words.
ISP = Internet service provider
SSID = is you broadcast NAME or service set identifier
RF = Radio Frequencies. (RFI , is interference)
3/4/5G (see wiki on 5G) and can fall back as used to 3G  and even below that. This is Wireless comm;'s not wifi  (Wireless is long range , wifi is 100meters max mostly way less)
ISP = internet service provider be that Dial up, Cable modem,  Verizon? 5G, FIOS , or SAT.
Jamming , any source on or near your channel band (RF) or by harmonics , that is by accident or on purpose  (lots or toys do this by accident, RC radio control cars, wireless land line telephones)

Now a top reasons to fail wifi list:
  • The PC's wifi card is missing, yah really. (look)
  • The PCs wifi driver is missing or corrupted or obtained not from or your OEM PC maker,but some endless and inane hacker/cracker/scalper web sites.
  • You forgot your credentials. SSID or Password.
  • The PC is infected with Virus/Malware.
  • Your ISP owns your router and wifi boxes and never told you your credentials.
  • You own your wifi router but failed to set it up right.
  • You didn't pay your ISP bill and they shut you down.

version 3  11-19-2017    ( revised 5-1-2019)