Constant problem with security certficate on a totally safe site I've used for years

Please explain the problem in detail. What happens? Error messages?

I've been a member of a forum about Poldark and the book and TV series for several years.

They recently changed the site over from http://poldark.activeboard.com - to - https://poldark.activeboard.com which immediately made all the icons down the left hand column disappear to be replaced by a grey blank space. Now saying in a small box in the top right hand corner that the site is not secure which is really strange as it's never happened before.

Can you help please thanks....

What is the exact error message?

I tried both links and had no problem.

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

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

http://kb.mozillazine.org/Error_loading_websites

https://www.bing.com/search?q=web+site+access+denied

Very odd as I've never had the security software you mentioned only Zone Alarm which I've had for years too, long before the https appeared.

So I had another look and tried clicking the shield to see what would happen, then saw a panel saying "disable tracking protection" which I did. Then a notice saying that "Firefox is blocking parts of the page that may track your browsing" and "you have disabled protection".

Suddenly all the icons appeared, then disappeared when I enabled the protection again....????

This may answer some questions; https://support.mozilla.org/en-US/kb/tracking-protection Tracking Protection