I’m posting because I couldn’t find anything that specifically spoke to this issue and thought that it might be good for posterity.
I already had The Office (US) and just added The Office (US) [Superfan]
Plex didn’t appear to be seeing the newly added Superfan folder. I have everything named according to Plex conventions. I scanned, analyzed, refreshed metadata, restarted and about everything that I could think of including to check the integrity of the database, etc.
I went into the original The Office (US), into one of the season folders and Get Info on one of the episodes. There I could see TWO entries, one for the original Office and another for the Superfan.
I used the Split Apart option on the 3-dot menu and sure enough, the Superfan folder and episodes immediately showed up and are available now to watch.
This was a hassle, I hope this information helps someone.