How do I get Plex to see second disk/part to movies?

The Lord of the Rings: The Fellowship of the Ring (2001) <—is the name of the movie at TMDB.

You have added a dash in place of the semicolon. Add NOTHING to a file name - simply leave out what you can’t put in a file name - like a semicolon:

The Lord of the Rings The Fellowship of the Ring (2001) <— like that

there’s no space between the dash and the tag.

I’d fix that to see what happens after a Plex Dance - and both Movie and Folder need to be exactly the same name - the correct same name.

Do two part movies work in individual folders - or do 2 parters need to be in the same folder? I don’t really know, but if you’re trying things, try that with the folder containing both movies named this:

The Lord of the Rings The Fellowship of the Ring (2001)
…The Lord of the Rings The Fellowship of the Ring (2001) - part1
…The Lord of the Rings The Fellowship of the Ring (2001) - part2

https://support.plex.tv/articles/naming-and-organizing-your-movie-media-files/