Plex is very picky with TV shows. You must follow the recommended file naming and organization.
/TV Shows
/Show Name
/Season 01
Show Name - s01e01 - optional episode name.ext
Show Name - s01e02.ext
See Naming and Organizing TV Shows
Also, some shows have different show names, episode names, or episode order based on air dates, DVD/Blu-ray packaging, etc. Plex matches against thetvdb.com. Use their episode names & order. Example: Spooks from BBC aired in US as MI5. Plex wants to see the show as Spooks, since that is the name in TheTVdb.
Edit / Addition: You’ll also need to Plex Dance the files if you change the names & structure.
