Update to the latest public release for your Plex Media Server (version 1.19.3). After updating you might need to reboot the server.
Edit:
If the QNAP cannot be updated beyond version 1.16.x you might need to wait for some kind of fix (and consider disabling automatic updates for your clients).
Thanks for the quick response. Yes, I assume it is a bug in the App update not working with older server versions.
The issue I have is that these servers are maintained and released by Plex. QNAP just distribute the update, and the end-user can only update to what is available,
New features are great, but maintaining backwards compatibility and regression testing should be a priority.
I’m not sure that’s correct. From what I’ve understood you can manually upgrade your apps in the QNAP app center (even through a terminal connection).
Latest version of Plex for WNAP can be found/downloaded here: https://www.plex.tv/media-server-downloads/
I know I can manually update the QNAP Plex App. But my question is why should I (or others) have to?
To try to make an analogy: on Android you can side-load an App or you can get it from the Play Store, but pretty much everyone gets the App and its updates from the Play Store. Why release the App as a side-loadable package, but not update the Play Store version?
Is it Plex or QNAP that have dropped the ball? I thought QNAP just ran the store and Plex made the packages (which would seem to be true given the link you provided).
Plex have just released a hot fix to their clients for iOS and Apple TV that should address this issue. Still… if you’re not willing to keep your server up to date you should also disable automatic software updates for the clients to avoid the same situation if the clients actually need a newer server.