You can't trust self-signed certificates on iOS with a validity period greater than 398 days

Self-signed certificates with a validity period greater than 398 days cannot be trusted on iOS and Firefox will not display a warning and instead fail to load the site.

If you've created some self-signed certificates for your home lab, and used a long validity period, like the 15 years mentioned in my How to create a valid self-signed SSL certificate for your internal services using PowerShell post, then you've probably encountered this issue if you are trying to import the CA root certificate into your iOS device. You are following the Apple guide Trust manually installed certificate profiles in iOS and iPadOS, you're able to import the certificate profile but nothing appears under Certificate Trust Settings. Also, if you're using Firefox on iOS, whenever you access a site that is using one of these self-signed certificates, instead of receiving a warning about the certificate being invalid, the page just won't load.

This is happening because your self-signed certificate (and I believe root CA certificate) likely have a validity period greater than 398 days, so you will need to recreate those certificates.

You can find more information about this at the link below:

About upcoming limits on trusted certificates - Apple Support
In our ongoing efforts to improve web security for our users, Apple is reducing the maximum allowed lifetimes of TLS server certificates.