Missing item from Library

Under some circumstances, NAS devices can be intolerant of special characters.
I’d try to avoid the é in the file and folder names.
Use Cache (2005) - {imdb-tt0387898} instead.
Then perform the Plex dance with the file.

Verifying that the file is playing at all (e.g. using VLC) is also a good idea.

Which type of computer are you using to access the NAS?
Is it a Mac?