I was seeing the same. This Plex release takes ages on first boot as it has to do a DB migration afaik. Leave it alone for a bit and it should come back up. See: https://forums.plex.tv/t/plex-media-server/30447/467 "Database changes may cause longer than normal start-up times after initial installation of this update, especially on larger libraries. Please be patient and do not interrupt this process."