I noticed that Plex can’t find media in a specific folder on my OMV NAS
The same happened to a friends Rockstor NAS so I setup a ubuntu server to test it.
I installed Plex and Jellyfin
Plex still refuses to see the contents of that folder while Jellyfin put it in the library properly.
its not a permissions problem, all set to 777
I can’t undrestand what is going on
Finally I got it
It is a naming issue
The name of the episode should contain season an episode number S01E01
Jellyfin can read the contents without the above, only with the episode title

