An error occurred during a connection to example.org. The page you are trying to view cannot be shown.
More details should be provided please, not just a generic "Secure Connection Failed" error page with a generic link to the generic https://support.mozilla.org/en-US/kb/secure-connection-failed-did-not-connect page. I'm sure the information there is well-meaning, but it will never be useful in diagnosing a specific problem if you obfuscate the details of the error from the user with bland, generic error pages and/or messages.
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Please provide a public link (no password) that we can check out. No Personal Information Please !
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