Although it’s happening a bit less recently, every once in a while when I add new media to Plex, the metadata does not appear. When this happens I first try doing the usual things like manually refreshing the metadata and emptying the library trash. If it’s still not working, I’ve found that manually deleting the cache files from the computer running the Plex server seems to almost always fix the problem.
I recently had to reformat my Windows PC and do a fresh install of Windows 10. One of the primary uses for this PC is to run my home iTunes server, but soon after the reformat, it became clear that something was not right with iTunes.