Hi mkwthomas, the most common reason for users to get secure connection errors with legit sites is related to their security software: it intercepts their browser traffic for filtering, and Firefox isn't set up to trust it.

This article covers that scenario in more detail:

How to troubleshoot security error codes on secure websites

Does that get you closer to a solution?

If not, let's investigate further. The error page should have an "Advanced" button which displays more technical information about the error. Could you copy/paste from that section into a reply?

Hi jscher,

Thank you for your reply. Unfortunately I had run across that article prior to posting my question. The antivirus and malware scan produced nothing. If I go to IT they will just remove Firefox as they have a preference for IE.

The "Advances" button produces the following additional information:

"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"

Thank you in advance for any additional help you can provide!

Could you try clicking the "SEC_ERROR_UNKNOWN_ISSUER" code; it should open a further section of the page. Ideally, it would have a large block of gibberish, which is a coded version of the certificate that Firefox finds to be fake. In that case, please click the Copy button and paste it into a reply here.

If you don't see that gibberish section, you can investigate using a different site that is a little less demanding with its security. For example (my site):

https://www.userchrome.org/

Do you get the error there?

Assuming so: click the Advanced button, then click the "Add Exception" button (see first screenshot below). 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.

On that site, the "Issued by" section shows me "Let's Encrypt Authority X3". What do you see there?

(These example screenshots are from a test page, not my site)

Unplugging from my network corrected the issue.

mkwthomas said

Unplugging from my network corrected the issue.

Thanks for the update. (I don't know why that worked, but perhaps it triggered a script your IT distributes to run at login.)