(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.