Hi Bob158, can you mention what OS you are running on that system (Windows, Mac, Linux)?

Did Firefox suggest that you perform a Refresh -- you would notice lots of settings changes -- or was this the only significant change during the update?

This is our general support article on this problem: What do the security warning codes mean?

When you click the "Advanced" button on the error page, Firefox usually displays a code starting with SEC_ERROR. This article covers the code users report most often: How to troubleshoot security error codes on secure websites.

Does that help with your error code? If not, could you copy/paste the "Advanced" details text and error code into a reply? Thanks.

I use Win10. Performed Refresh - No help! Reviewed "Your connection not secure" and opened "Troubleshoot...error message." - no help! I have used Firefox for years and never had any problem until this latest version. Need a fix now! (Note: A pasted Text message of Advanced on "your connection is not secure":member.trsil.org 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 I need a fix now! Thanks Bob158

Hi Bob158, please click the SEC_ERROR_UNKNOWN_ISSUER code to open a panel showing a coded version of the certificate Firefox finds unacceptable. Copy that (there should be a button to copy it) and then paste it into a reply. A support volunteer can decode it and see whether that helps identify the source of the problem.

https://member.trsil.org/subsections/secureaccountaccess/security/signin.aspx Peer’s Certificate issuer is not recognized. HTTP Strict Transport Security: false HTTP Public Key Pinning: false Certificate chain:

So if you click the Advanced button, then click on the SEC_ERROR_UNKNOWN_ISSUER code, a panel should open with a large block of gibberish-looking code. That's what I need now.

The sample image below has blocked out the certificate for this example.

Hi Bob158, if the first method didn't work, could you try this second method?

In the "Advanced" section, click the "Add Exception" button (see first screenshot attached). We're not really going to add an exception, but we can get a better view of the certificate here.

In the Add Exception dialog, click the "View" button to pop up a certificate viewer. The interesting part is the "Issued by" section. I've marked that on the second screenshot for reference. What do you see there?

Thanks to everyone that gave a response to my problem. I am happy to report the problem is solved! I use Kaspersky virus protection and for some reason it was not allowing any website to open, but gave an error message, Your connection is not secure. The solution from https://support.mozilla.org, How to troubleshoot the error code "SEC-ERROR_UNKNOWN_IS..." for Kaspersky: Open dashboard Click Settings bottom left Click Additional, then Network In Encrypted connections scanning section check "Do not scan encrypted connections options" and confirm change. This worked for me; however several other virus products are listed in the article which may work for others. Thank you Mozilla for addressing my problem without delay! Bob158