Clean OS X install, my PlexMediaServer content is gone - How to restore PMS from Apple’s Time Machine using raw backup files straight from the backup drive

Plex Media Server
6

The preferences file contains a number of „machine identifiers“. Those will have changed during the reinstall of your Mac.

  1. stop the Plex Media Server
  2. remove the various machine identifier properties from the preferences (see: Plex not finding libraries after restore from time machine and Big Sur update - #9 by Volts)
  3. restart your server

I don’t remember if this will require your server to be reclaimed but it should be fairly straightforward from there.