If you have recently done a "major" windows update, Windows Defender Firewall may have revoked your privileges. Try the following: Open Control Panel Select "System and Security" Select "Windows Defender Firewall" Select second option on left side of screen-"Allow an app or feature through Windows Defender Firewall" Scroll down until you find-"Firefox (C:\Program Files\Mozilla Firefox)" Make sure both boxes have a check mark. If not, select "Change Settings" tab and then mark box.

[You may also repeat this process if an app or program has problems running as well.]