Plex can be picky about naming and organization, especially when it comes to subtitles and TV shows.
Follow Plex’s Media Preparation guidelines.
For movies: Naming Movie Files
It is best to use nested folders, with one movie per folder. For example:
/Movies
/Avatar (2009)
Avatar (2009).mkv
/Batman Begins (2005)
Batman Begins (2005).mp4
Batman Begins (2005).eng.srt
Plex is more strict when it comes to TV shows. See Naming series & Season Based TV Shows.
The desired structure is:
/TV Shows
/Grey's Anatomy
/Season 01
Grey's Anatomy - s01e01.avi
Grey's Anatomy - s01e02 - The First Cut is the Deepest.avi
Grey's Anatomy - s01e03.mp4
/Season 02
Grey's Anatomy - s02e01.avi
Grey's Anatomy - s02e02.mkv
Grey's Anatomy - s02e03.m4v
After making any changes you’ll need to re-scan the library. You may also have to perform the Plex Dance if a re-scan does not pick up the changes.