Last week I fixed a few by the following methods.

1. Went to Device Manager and went to the Network Adapters then expanded that tree. I then right clicked on the Eithernet then selected uninstall device. I did NOT uninstall/remove the driver files.
Repeat for WiFi.
Now use Action, Scan for changes an re-test. May need to reboot.

2. On another PC I had to forget the old networks. Old would also mean these networks that you can't connect to. How to forget WiFi connections is on the web.

3. And a failed internal WiFi card. Had to pull out an USB WiFI stick and that fixed that machine.