Windows clients lost synchronization settings

I have several users running Windows seafile clients. After I did some server maintenance (details see below) all the clients forgot about the synchonizations settings and stopped synchronizing. The cloud which usually is green for synchronized librariers turned back to ‘not downloaded’ and this happened to all clients.
This is what I did on the Seafile server: I created a full backup of my system using dd and copied the whole partition to a new one. To test if the backup is fully working I bootet my Seafile server into the new partition and the server came up successfully. Because the backup system was using the same SSL certificate and IP address the windows clients connected to the new server.
Then I rebootet the server and turned back to the original partition. After this procedure the Seafile clients stopped the synchronization.
Any idea why this happened? Where do the clients store the information which folders to synchronize?

Seafile Server v7.0.5

Appreciate any help.