Maintenance mode after RAM extension

Hello all,
I have shut down the server and installed a RAM extension. RAM is recognized in BIOS, server starts normally.
Data directory is on an external hard drive. I then mount this to the appropriate path.
If I now call the NC in the browser I get the following error message:
This Nextcloud instance is currently in maintenance mode, which may take a while. This page will refresh automatically when Nextcloud is available again.
All the help mentioned in the forum has not yet led to success.
Nextcloud is installed on an Ubuntu Server 20.04 LTS via snap. I have not initiated an update.
in config.php it said maintenance => true, I set it to false. But even that did not bring any change.
But when I call NC again in the browser, the config.php again says :
maintenance => true
Does anyone have any idea?

ok, now after a while I have again the command
sudo nextcloud.occ maintenance:mode --off
and got the following response
Maintenance mode disabled
And now it works again, whatever it was.