Network shares that you’ve authenticated into, for example an AFP share named “MyNasFilms” would get mounted like this:
/Volumes/MyNasFilms
You may just need to follow The Plex Dance because you’ve moved things or altered how things are organized, but your database was not massaged to reflect those changes.
For organizational purposes, because PMS searches all subdirectories below the one that’s at the top of each Library path, I never let films live below music. Do you have that happening?