Power of the googles! Plex server stop downloading the movie posters for anything added new or old. I thought maybe it was a ploy to get people to upgrade to Premium but ended up being something easy to fix.
Check out this post and rename the folder it suggests:
https://forums.plex.tv/discussion/158312/missing-movie-posters
This is the folder:C:\Users\[WINDOWSUSERNAME]\AppData\Local\Plex Media Server\Plug-in Support\Caches\com.plexapp.agents.themoviedb