server non reachable after upgrage

Hi to all,
since some month I have a issue with plex server on my mac. If i upgrade the server app, plex stop works from every player, the server seems to be offline. So the only way to use plex is to restore the old server app ( 0.9.15.6) . This version is the last I can use.
I don t no how to fix it.
thank you .