I found this same problem after installing the latest nicrosoft update. I uninstalled that update and all is working agian. Hope this helps. Seems Microsoft have cracked down on granting permissions - something to do with some sites having no certificate and Microsoft doesnt like that.

Did you try with Firefox in Safe Mode? https://support.mozilla.org/en-US/kb/diagnose-firefox-issues-using-troubleshoot-mode#w_how-to-start-firefox-in-4troubleshoot-modesf5safe-modesf What security software are you running?

Sandy, I got an error trying to uninstall update KB5021233.

PR_CONNECT_RESET_ERROR means that something in the connection closed the connection. This is usually not Firefox although an extension might be involved. This is more likely caused by security software on your computer.

Boot the computer in Windows Safe Mode with network support to see if that has effect.

• https://www.bleepingcomputer.com/tuto.../how-to-start-windows-in-safe-mode/
• https://www.digitalcitizen.life/4-ways-boot-safe-mode-windows-10/

In my case it turned out to be the most recent microsoft update. Seems Microsoft is now blocking access to sites without a secure connection certificate. I uninstalled the update and everything works again. Thanks all for your help