Hi, you don't say exactly what you've tried, so please see if anything here helps - Secure connection failed and Firefox did not connect.

If you are still having a problem, try deleting all references to the website in question, as shown under the heading 'How do I remove a single website from my history?' in this article - Delete browsing, search and download history on Firefox, then try the site again.

If your question is resolved by this or another answer, please take a minute to let us know. Thank you.

If you can't inspect the certificate via "I Understand the Risks" then try this:

Open the "Add Security Exception" window by pasting this chrome URL in the Firefox location/address bar and check the certificate:

• chrome://pippki/content/exceptionDialog.xul

In the location field of this window type or paste the URL of the website.

• retrieve the certificate via the "Get certificate" button
• click the "View..." button to inspect the certificate in the Certificate Viewer

You can inspect details like the issuer and the certificate chain in the Details tab of the Certificate Viewer. Check who is the issuer of the certificate. If necessary then you can attach a screenshot that shows the certificate viewer.

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

If you have Avast then try to disable HTTPS scanning in Avast Web Shield.

• http://www.ghacks.net/2014/10/31/avasts-https-scanning-interferes-with-firefox-and-other-programs/
• https://forum.avast.com/index.php?topic=176073.0