I have an older imac (2008) that no longer receives updates, so the only way I could get Plex to work was to use a version no later than 1.31.3. I got a new iMac and tried to load Plex with no luck so I decided to use the migration assistant which transferred all my old files to my new iMac. Now the new Mac acts like the old one. When I try to load the latest version of Plex the symbol appears for a few seconds in the top right hand corner of the screen, then disappears, and Plex won’t recognize my server or any of my files. I’m ready to wipe the computer clean again and just delete all my plex files and start over from scratch. Any suggestions to make this easier before I do this?
Migration assistant and Time Machine backups can end up with a messed-up database.
Try following the guide from this support article to transfer your setup.
https://support.plex.tv/articles/201370363-move-an-install-to-another-system/