Local Plex Server Unavailable

[co9295]

My plex apps are unable to access my local Plex server. I really would appreciate some help.

I’ve been running Plex on a TrueNAS server for about a year without any significant problems.
Because I was unable to update Plex due to some TrueChart reason, and my Plex was getting old I thought it was a good idea to remove my old Plex server, update TrueNAS to Cobia, and then install Plex from the TrueNAS charts.

So everything went pretty fine. I can open the Plex Web Portal via ip address on my local network, see my media library, and play the media inside the browser. I deleted my old server in the account, and my new plex server is in the authorized devices. So I thought all was good.

However when I use any app (tablet or nvidia shield) it is not able to access my Plex server.
To test I have temporarily enabled remote access. My network is not setup for outside connections. But that did make the plex app see the media library and use indirect access to playback something. Since I only want direct connections on my local network I have disabled remote access again, and now see that my local plex is currently unavailable.
So what can I do to make my plex apps be able to access my local plex server again?
How does the plex app get the connection information to find the local plex server?
I found this support article
https://support.plex.tv/articles/204604227-why-can-t-the-plex-app-find-or-connect-to-my-plex-media-server/
but did not see anything that helped me. I used default settings, and I do not require secured connections.
Does the app use different ports than the web portal (32400)?

I’m looking in the plex server log and I see a message “Sending Server Info” with my public internet IP address and port 0. Is that as expected?

[co9295]

So if anyone finds this post and struggles with the same problem… here is the solution and explanation.

First the tl;dr solution. Use the custom server access URL in your plex server settings under network.

Explanation:
Plex apps uses GDM to discover local servers on the network. You can see if this is enabled in your plex app settings. Furthermore in your plex server settings under network you can see if local network discovery is enabled. GDM uses ports 32410, 32412, 32413, 32414
The problem is that TrueNAS Plex only opens port 32400. I uses TrueCharts before, so that might have opened up more ports, so I did not encounter problems before.
Perhaps there is a way to open up more ports in TrueNAS Plex, but I did not see any way to do this.
Instead I have disabled GDM and instead entered the custom server access URL in the plex server network settings (advanced). That’s the same base url as I uses to access the web UI.
Problem solved.