Why does the  error "An unknown error occurred" occur in the DocuWare Desktop Apps? 
Also, the DocuWare Import configurations are not loaded in the "Scan" tab, in the DocuWare Desktop Apps., There is only an empty drop down menu shown and in the DocuWare Desktop Apps the Scan-Button is grayed out.

Please check whether the DocuWare Desktop Service User (default: Local System) has access to all "My Documents" directories of the users working with the DocuWare Desktop. If the "My Documents" folders are not available locally, for example it is a mapped folder, the Local System account can not access them and will display the message mentioned above. To solve this you can either change the DocuWare Desktop Service user to a user that does have access to the network share or you can change the "My Documents" folders location so that they are available on a local drive: (e.g. C:\Users\...).

Now, if the solution is not appropriate for your operation please create the following logging: "Traces DS.svclog".

To enable this log, open the "DocuWare.DesktopService.exe.config" file with Notepad. You will find this file in the DocuWare Desktop program directory.
Find the end tag "</configuration>" and copy this section just before that tag. This is easily done by positioning the cursor at the start of the end tag line and then pressing enter. This will create a blank line. Copy the text in to the blank line.

            <source name="System.ServiceModel"
               <add name="traceListener"
                   initializeData= "C:\Temp\Traces-DS.svclog" />

Ensure that there is a folder on C:\ called Temp, or alter the path to a location of your choice.
Save the file and restart the DocuWare Desktop Service.

After resproducing the behavior, please send the log to DocuWare Support.