When plex looks at the files for the first time, it has to determine what show it is. It looks at the folder name and basically does a search on TheTVDB.com for that show. If the folder matches closely to what it finds on TheTVDB, it decides THAT is the show.
Then, it digs into the subfolders within, and starts looking for files with SxxExx format in their name. Whatever it thinks the show is, it picks any file numbered like S01E01 in their name and decides that is season 01 episode 01.
If Plex sees two “90 days Fiance” folders (or closely-named shows) in your TV shows folder, it might think they are both the same show, and thinks you might just have two copies of the show. Despite naming the individual files “90 days fiance” it doesn’t matter, since the folder itself got matched to a different show.
Basically, the best success is to set the folder itself to match - as closely as you can - to the display name on TVDB. In particular, 90 Day Fiance (2014) and 90 Day Pillow Talk (2019). Use those names as the folders and you are likely to have success with Plex matching them automatically and separately. It’s now a good idea to include the release year of the show as well. It’s hard to find the year of the show in the page itself for a show, so do a search, the search results will have the year it came out. (Like this search.)
Make sure to do the Plex Dance. Move the folders somewhere that Plex is not looking at. Change the names of the folders. Re-scan the TV Show Library. Empty Trash. Move the newly-renamed folders back into the location. Scan. They should show up separately.
