Might want to change your tags at the top to move this to Plex Media Server.
First can you confirm that you are using the OMV Plex Plugin?
The plugin worked up til 1.15, with no one maintaining it you have a couple of options that will take a bit of effort:
1 Fix the plugin (probably not going to happen)
2 Normal Plex install (backup your databases first)
3 Migrate to docker (backup your databases first)
4 Create your own systemd override for Plex
The plugin is basically an override, I can’t pull it down right now to look at it.
To get an idea of what to do have a look here:
