SSL Initialization Error on App, but not via Browser

I have an Apache server with mutual SSL on a self-signed CA. The server itself is working fine, and I connect to it from my cell phone [yes I already added the CA to my trusted agents]. Even the Nextcloud server is working when accessed from my cell phone web browser. For example: https://<My.I.P.Address:<myport>/nextcloud … brings me to the login page.

However, when I put the same inside the Android app, I get: SSL Initialization Failed

The httpd-error.log doesn’t show any errors and there’s nothing in nextcloud.log. Why would the Android app treat SSL verification any differently than the web browser? I even tried adding a bunch of old SSL Ciphers but that did nothing.

Server: apache2.4 ; php81-25
Cell Phone: Pixel 6 ; Android 13 ; Nextcloud 3.22.2

Edit: One more thing. When I disable SSL entirely, the app connects to the login page. So apart from SSL, my config appears good.

Edit2: I made sure to set the CommonName for the CA cert and server cert to ‘nextcloud’, same as my vhost ServerName.