My PC WiFi automatically turns off and refuses to turn on

(I am assuming that you are using Windows)

First, you should try and run the Windows Network Troubleshooter (Start button > Settings > Network & Internet > Status. Under Change your network settings, select Network troubleshooter) This is what Microsoft recommends.

If that doesn't work, you should look at the prtscr key on your keyboard. Underneath there should be a telecom tower icon. Try pressing fn + prtscr and then try to turn your wifi back on. You might have accidentally pressed it.