Self-signed certificates on iOS (Apple) are limited to 825 days
Some of us want to do self-signed certificates and want to set it and forget it so we set expiration dates that last a really long time. At the same time we're setting up vaultwarden and our own root certificates for the very first time, so when things don't work we don't know where to look. Don't overlook the self-signed certificate you issued for vaultwarden. If you or a tool (on your behalf) issued a certificate that is valid for more than 825 days, iOS automatically considers it invalid/not trusted even if you have everything setup and installed correctly.
Hope this helps some of us that run into certificate issues. It's easy to find the validity period for public certificates but it's harder to dig up how long Apple's validity period is for self-signed certificates.