Some problems occur when your Internet security program was set to trust the previous version of Firefox, but no longer recognizes your updated version as trusted. Now how to fix the problem: To allow Firefox to connect to the Internet again;

• Make sure your Internet security software is up-to-date (i.e. you are running the latest version).
• Remove Firefox from your program's list of trusted or recognized programs. For detailed instructions, see

Configure firewalls so that Firefox can access the Internet. {web link}

This could be a problem with the DNS server or by using a proxy or VPN that is not available.

You can use the DNS Lookup tool on the about:debugging about:networking page to test your current DNS service. You can possibly switch on DNS over HTTPS (1.1.1.1).

• https://support.mozilla.org/en-US/kb/firefox-dns-over-https
• https://support.mozilla.org/en-US/kb/dns-over-https-doh-faqs

• https://support.mozilla.org/en-US/kb/websites-dont-load-troubleshoot-and-fix-errors
• https://support.mozilla.org/en-US/kb/firefox-cant-load-websites-other-browsers-can
• https://support.mozilla.org/en-US/kb/firefox-and-other-browsers-cant-load-websites

'(edited to link to the correct about:networking page)

Thanks FredMcD and cor-el. I tried both resolutions to no avail. However, I have solved the problem myself. Thanks again:)

PC

That was very good work. Well Done.

Please tell us how you fixed the problem as this can help others with similar problems. Then flag that post as Solved Problem