Are other movies you’re adding to that library showing up ok?
Its possibly getting matched as a duplicate to another title already in your library
In the library view go here and filer by duplicate

Click the 3 dots on the poster and select “get info” It will tell you what the titles are named in your file system
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You can split apart and rename/fix match them
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You can fix the naming issue whatever it is. You can input the tmdb or imdb id number on the file in curly brackets to get an exact match
example:
The Matrix (1999) <-folder
The Matrix (1999) {imdb-tt0133093} <-file
You may have to plex dance <-click