Hi albert2910, glad to see you on Mozilla Support Forum.

• Open a new window in Firefox and type "about:config" without the quotes and hit enter.
• Confirm that you want to continue.
• In the search field, type in security.enterprise_roots.enabled and hit enter - you'll be left with one field.
• If it's marked as "false" then double-clicking it should turn it to "true".
• Close the window, then go back to your website try again. For me, this worked *perfectly*!

If it doesn't solved your problem, then feel free to ask in Reply Section. Thanks for raising you question in Mozilla Support Forum.

Entering the web site gives me this:

Hi albert,

• open "options" > "Privacy and Security" > "Deceptive Content and Dangerous Software Protection"
• unable the field "Block dangerous and deceptive content"

WARNING: if you do this, Firefox can't warn you about dangerous content any more

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

What do the security warning codes mean