Problem with Connection via Internet - Fritzbox 6490 Cable

Hey guys,

I got a new fritzbox and now I have problems with my Plex server.
I want to reach my server from my mobile phone.

But in settings there is:
"Nicht ausserhalb Ihres Netzwerks verfügbar
Ihr Server ist bei Plex angemeldet, aber außerhalb Ihres Netzwerks nicht verfügbar."

And in the app, there is a "indirect" connection.
I opened port 32400 (TCP) and I activated UPnP, but that didn't solute my problem.

I need help...