Please provide a public link (no password) that we can check out. No Personal Information Please !

There is security software like Avast, Kaspersky, BitDefender and ESET that intercept secure connection certificates and send their own.

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

https://support.mozilla.org/en-US/kb/secure-connection-failed-firefox-did-not-connect

https://support.mozilla.org/en-US/kb/websites-dont-load-troubleshoot-and-fix-errors

What do the security warning codes mean

This could be about forcing secure HTTPS on a website that only works with HTTP.

• /questions/1353385 Cloudflare is blocking one website for the rinconbeach.com hotel. Error 404

the site I am trying to connect to is rcdiy.ca

I turned off avast antivirus program. still no connection

Problem Solved I went to settings and made an exception to "Enable HTTPS-Only Mode in all windows" for the web site that I could not connect to. Now it connects. But what puzzeles me is why did it work for such a long time and then it didn't? Oh well, it works now

Thank you to everyone who took time to offer help and suggestions Roger

That was very good work. Well Done. Please flag your last post as Solved Problem as this can help others with similar problems. Go to that post and click the 'Solved' button to its right.