Several error messages in the client after server relocation


I had to move my NC (20) to a new server. That worked out well so far. But now I always get the following error message with many small files (15 KB - 282 KB):

PathToFile: Connection closed

Furthermore also a few times I have this issue:

The downloaded file is empty, although the server has reported {File size}.

The client also says “There are unresolved conflicts. Click for details.” - I can click what I want, there are no details.

The client version is Nextcloud Desktop Client Version 3.0.2 (Windows)

I only have the error messages in German. I hope I have translated them understandably.

Does anyone have an idea how I can fix the bugs?
Before the server move, everything worked correctly.

Help is really appreciated!

Kind regards,