Screen shot of the error and what you were doing when the error happened? Others have to be able to replicate the error to know what is going on.

This is what I get. I do not get the option to add an exception.

Your connection is not secure

The owner of www.google.com has configured their website improperly. To protect your information from being stolen, Firefox has not connected to this website.

This site uses HTTP Strict Transport Security (HSTS) to specify that Firefox may only connect to it securely. As a result, it is not possible to add an exception for this certificate.

Learn more…

Report errors like this to help Mozilla identify and block malicious sites

www.google.com uses an invalid security certificate.

The certificate is not trusted because the issuer certificate is unknown. The server might not be sending the appropriate intermediate certificates. An additional root certificate may need to be imported.

Error code: SEC_ERROR_UNKNOWN_ISSUER

It sounds like some other software is interfering with the connections. Norton and the likes are very aggressive A/V that it can block the connections causing the warning your getting.

Nothing changed on my computer except I “Refreshed Firefox” earlier. I’ve been using it for many years with no issue. I use Kaspersky for my anti-virus.

Hi, it is your Kaspersky. There is security software like Avast/AVG, Kaspersky, BitDefender and ESET that intercept secure connections and send their own certificate. Which gets rejected.

• 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://support.mozilla.org/en-US/kb/troubleshoot-SEC_ERROR_UNKNOWN_ISSUER

If you are running any of the above software please their community forum for a work around as to the settings should use. Update if it is available and reboot and try.

Please let us know if this solved your issue or if need further assistance.