I moved your post, as it is a different issue than where you originally posted.
The maintenance message is expected when updating to a new version of Plex Media Server and database migration is required.
Depending on the size of the database, the CPU speed, and the number of changes required, it may take minutes to hours for the migration to complete.
The web page does not auto-update when the migration is finished. You’ll need to occasionally reload the page.
A server reboot, or stopping/re-starting PMS, is not recommended. That just restarts the migration. It can also cause database corruption if the database is not closed correctly.
Know you’re back up and running. Wanted to let you know what happened and that is is expected.
lol that’s what plex says when it’s doing maintenance tasks like making database changes required for the update. So you basically killed the update as it was making changes… very dangerous.
Same issue with Synology NAS. This is not resolved by a restart.
Do not restart, just wait.
It took about 10 minutes on my DS1019+ after restarting and it came up.