If a movie is not appearing in any online metadata website, then it is very likely not “matched” inside of Plex. Which means it hasn’t been assigned to one of the ‘metadata agents’ of Plex.
Local extras in Plex are handled by the ‘Local Media Assets’ agent.
But if a media item doesn’t yet have an agent assigned, the LMA agent is not active. Thus it cannot scan for the extras.
If you cannot find a proper record for your video on any Plex-supported metadata service, use the ‘Match’ feature to match the item to the ‘Personal Media’ agent.
This should kick the Local Media Assets agent into working as well.
