Thank you tom, I just found out what happened. Since I used a software to rename the movies, it left the older folders in the same “Movies” folder and apparently it bothered Plex who probably scanned the files before they were renamed (I shouldn’t had activate the auto-scan), which then updated the folder, but not the “match”.
By the way, after removing the older folder, I had to do the Plex dance as you suggested.
Thanks a lot