Error `sec_error_revoked_certificate` when viewed in Firefox only

An update to ARJUN KP's answer, which works with Firefox Quantum, v68:

• Open Firefox options
• Privacy & Security
• At the bottom, under Certificates, uncheck: "Query OCSP responder servers to confirm the current validity of certificate

When Firefox web browser checks a security certificate, it also checks with the issuing authority if the certificate is valid. It appears that, near a certificate’s expiration date, the issuing authority may release a new certificate. The two certificates have conflicting expiration dates.

For reasons unknown, this caused Firefox to report a sec_error_revoked_certificate error and refuse to allow you to connect to the site!

You can go through the following steps, but it will reduce the security.

1. Firefox main menu -> edit ->Preferences
2. click on Advanced Tab
3. select certificates
4. click on validation
5. Uncheck the option "Use the Online Certificate status protocol(OCSP).........."
6. Click OK button

Now you can see the page with out error.

The instructions provided in the answer by Arjun KP don't work for more recent versions of Firefox (tested on v. 57.0.1). Instead, here's what I did:

1. Enter about:config in the address bar, accepting the risk if prompted.
2. Enter security.OCSP.enabled in the search bar.
3. Change the value of that setting from 1 to 0.
4. Reload the page that failed.

After doing this, my site started working.

However, as Arjun mentioned, this will reduce the security of Firefox, since it disables the Online Certificate Status Protocol. Ideally, you should reset the setting to 1 after you finish with that site, and not load other pages while it is set to 0.