I am on Linux Mint, Firefox 100.0 and I am trying to access a website, https://www.citapreviadnie.es:38188 (requires personal DNIe certificate). However, I keep getting SSL_ERROR_UNKNOWN_CA_ALERT. If I view the certificate of the website, 1. Firefox doesn't tell me which part of the chain is invalid or not trusted (or I don't see it) 2. When I try to download and import each of the CA certificates, I get an alert saying "This certificate is already installed as a certificate authority." 3. If I try to import the whole chain, I get another alert telling me "This is not a certificate authority certificate, so it can’t be imported into the certificate authority list." 4. If I try to add a permanent exception to the site, I see "This site attempts to identify itself with invalid information", but if I click "view certificate" I'm back to step 1, and adding the exception does not have any effect. What am I supposed to do now?