You’re following the correct procedure for rolling back to an older version on a Mac. How far back are you going?
Try renaming your Plex data folder (~/Library/Applications Support/Plex Media Server/) to something else temporarily; then try to start the rolled-back version of Plex Media Server. It will create a new one, basically giving you a blank slate for testing. (You can always delete the new on and move your old one back).
If that works, it likely means that there’s something in your existing Plex data causing the older version to behave the way you describe; otherwise, there’s something more fundamental causing the startup issue. In either case, logs from one of these startup attempts may be helpful.
On a side note, I had a look at your other recent post regarding Plex Media Server “crashing.” There’s another thread on the forum discussing something similar (server running, but inaccessible). There are some steps in the first post to see if you’re experiencing the same problem.
