Nextcloud or one of the apps require upgrade - only a limited number of commands are available You may use your browser or the occ upgrade command to do the upgrade Setting log level to debug Turned on maintenance mode Exception: Updates between multiple major versions and downgrades are unsupported. Update failed Maintenance mode is kept active Resetting log level
The maintenance mode has a special reason.
After upgrading you should have seen one or more messages, which commands have to be executed to turn off the maintenance mode. You should find concerning entries in the log files.
Make sure you log into nextcloud as administrator before any nextcloud upgrade and update any apps that need updating and correct any important items listed on the security and warnings page of the administration settings. Usually the items that really need to be taken care of before an upgrade are the db things as mentioned above. Some of the warnings can be ignored or are related to the docker apps web config and I have left those alone.
I haven’t had any issues with upgrades that I can recall as long as I check these things first.