Behavior:
During the configuration of Paper Scan a login into the organization is required. Then, if there is a message about incorrect login, please check the Platform logs (http://<yourservername>/docuware/Platform) . In that logs you probably will find a message like this:
Cannot find available organization. Check if there are valid licenses.
Solution:
This message indicates, that the DocuWare Mobile license is not available in the organization. In order to use Paper Scan, the DocuWare Mobile license is necessary.