Can't access some website.

I found more information. The DC in SSL_ERROR_DC_EXPIRED = Delegated Credentials. Facebook is a pioneer of using delegated credentials, which is said to be a more secure way of distributing certificates. ([https://engineering.fb.com/2019/11/01/security/delegated-credentials/ 11/1/2019 article]) Could you try clearing your Firefox web cache to see whether that makes any difference to this problem? This article has the steps -- just select Cached Web Content, don't delete all the cookies and site data: [[How to clear the Firefox cache]] Any improvement on the next try? ---- This was a hidden feature up to Firefox 89 but is now enabled. If we can't get it to work, here is how you would turn it back off: (1) In a new tab, type or paste '''about:config''' in the address bar and press Enter/Return. Click the button accepting the risk. (2) In the search box in the page, type or paste '''security.tls.enable_delegated_credentials''' and pause while the list is filtered (3) Double-click the preference to switch the value from true to false ''More info on about:config:'' [[Configuration Editor for Firefox]].