Please explain the problem in detail. What happens? What is the exact error messages?

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

Secure Connection Failed

The connection to volafile.org was interrupted while the page was loading.

   The page you are trying to view cannot be shown because the authenticity of the received data could not be verified.
   Please contact the website owners to inform them of this problem.

this is the message for all of them hope it clarifies the problem.

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-error-message

https://support.mozilla.org/en-US/kb/connection-untrusted-error-message

Websites don't load - troubleshoot and fix error messages

http://kb.mozillazine.org/Error_loading_websites

Sorry I do not understand what I have to do can you clarify how I get Firefox working as before, I have AVG free on my system but cannot see any problem there, the settings appear the same

Followed the troubleshoot from link below and still the same https://support.mozilla.org/en-US/kb/secure-connection-failed-error-message#w_avast-and-avg-security-products

Go to AVG Support Forum for a work around or get rid of AVG. https://support.avg.com/answers

Will have to try this next week internet connection down

on my other device with the problem

Thanks for all your help and advice, problem solved now.