No matter how I name them, not a single part of a tv serie, from dvd, is shown in Plex

Plex Media Server Metadata & Adding Files
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No, you did not. “Fargo 2 (2015)” is wrong. “Tru.Detect” is wrong.

Rename all the folders and files following the Plex documentation or the example in my earlier post.

Then Plex Dance the show, to clear the old names/matches from the Plex database.