SOLVED: IMDB support in 10.9.1

[mcarlton00]

The scanner expects to be given a directory that contains either movies themselves or directories matching the movie names.

https://jellyfin.org/docs/general/server/media/movies/

So in this case, the scanner expects to be given "Horror", and find either

Code:

Horror
└── Army of the Dead (2021).mp4

or

Code:

Horror
└── Army of the Dead (2021)
    └── Army of the Dead (2021).mp4

Adding other structures into the mix has a high likelihood of causing issues.

As for it working in 10.8, there's been 2+ years of changes going into 10.9.  Several changes to the parser to better support features, but that may have a side effect that it got more strict to your more freeform structure.