I am having the same problem
Checking the logs, I get:
Plex Plug-in [com.plexapp.system]: error while loading shared libraries: libpython2.7.so.1.0: cannot open shared object file: No such file or directory
Plex Plug-in [com.plexapp.system]: error while loading shared libraries: libpython2.7.so.1.0: cannot open shared object file: No such file or directory
/usr/lib/plexmediaserver/Plex Relay: error while loading shared libraries: libcurl.so: cannot open shared object file: No such file or directory