Plex connection from outside failed

Hey folks,
my problem is that i cannot reach my Plex server from outside. I tried to log in via Samsung tv from my girlfriends home but the server is not available.
I can reach the Server from outside with my iPhone. i can stream inside my network to tv tablet and iPhones. But from outside the server is not available from tv who works without firewall and is a smart tv with flex running on it.
What have i done till now?

  • First of all, i have a qnap TS-451A-4g running on a 400mbit/s internet connection via LAN.
  • i did already a port forwarding on port 32400:80 on my fritzbox router (tried to read all faq i could find in the last 2 months since i bought the NAS)
  • besides the linux running qnap i use mac hardware without any firewalls

What is weird is that i sometime get the server available on the plex media browser, but usually the next few hours or in the morning the servers is not available anymore, whatever i try.
For example turning off the port forwarding and on again doesn’t do any difference. The servers is not available.
i restart the qnap, the macbook, the router and nothing changes. Or sometimes the servers available but only for a short period of time, too short to test the connection from outside at my girlfriends home.

I wish i could make my library available for my family who lives in different parts of germany and europe, but i cannot

Maybe anyone has the same problem and can help me.

Right after the media server update today, i cannot connect to the server from outside, even not with the iPhone. (Sorry for bad english)