Error message instead of login screen


since a few days, i get an error message instead of the nextcloud login screen on my webspace:
**Downgrading is not supported and is likely to cause unpredictable issues (from to **
But I haven’t done an update or any other changes. The error came suddenly by itself.
Any ideas?

Thanks in advance

Please provide information about your server environment.

Which OS?
Which package management? Or manuall install?


i have installed the nextcloud package ( on a rented webspace at hosteurope (provider).
PHP Version 7.2 and a MySQL database.
Everything worked perfectly for about 1 year. Since a few days I get the error message.
Which information do you need and how can i find out?

Check the web server and Nextcloud log file for related messages which are being logged at the time of a login attempt.