Android app does not connect, every other Browser/iOS app working

I have installed an jitsi instance on my own server which is behind a NAT router. The installation I have done accordingly to the Self-Hosting Guide at the jitsi meet handbook.
I am using a wildcard certificate (*.domain.de). This is working for every browser local and connection from the internet. The jitsi meet app on an iOS device works fine.

On a Samsung Galaxy Tab A running Android 7 the app doesn’t connect to jitsi.
Info from the app when I want to connect: “The connection is aborted. Please check your network connection.” When I use the Google Chrome browser on Android and open the Connection as a desktop client it works fine.

At Wireshark I can see that the Android app get an “Certificate Unknown” alert.

Linux version: Ubuntu 20.04 LTS running jitsi instance

Does anybody have an idea where is the problem?

Thanks for your help.

Best regards

If your TLS certificate is issued by Let’s Encrypt, you may be suffering from a known issue: The Android app does not accept Let’s Encrypt certificates from the TURN server

Thank you for this information plokta. The problem with Let’s Encrypt I didn’t know yet.
My certificate isn’t from Let’s Encrypt, so that wasn’t my fault.

I have solved the problem. There was a fault in the chain of the certificate. Now it is working.