That is a problem with some of the CDN servers used by Microsoft and that needs to be fixed on their end. As a workaround for now you can disable OCSP stapling in Firefox, but since this is a security feature to check the validity of a certificate then best to only disable this if you get an error visiting MS websites.

See:

• /questions/1361257 Secure Connection Failed" (Error Code:sec_error_ocsp_unknown_cert)

Try to disable OCSP Stapling temporarily by setting security.ssl.enable_ocsp_stapling = false on the about:config page to see if that has effect.

You can open the about:config page via the location/address bar. You can accept the warning and click "I accept the risk!" to continue.

• https://support.mozilla.org/en-US/kb/about-config-editor-firefox

It is best to reset this pref via the right-click context menu to true once you are done with accessing an affected website since this is a security feature.

Hi

Just a quick note to ask you to look out for an update to Firefox that should be with you very soon that should resolve this issue.

If you have used a temporary workaround in about:config, I recomend that you reverse this measure at this time.

You can update to 95.0.1 via "Help -> About Firefox" to get a fix for this issue.

• https://support.mozilla.org/en-US/kb/update-firefox-latest-release

If you have modified security.ssl.enable_ocsp_stapling on the about:config page then reset the pref to re-enable OCSP.