With DocuWare 6.5 we introduced the option to enter user credentials for unattended activities. This user and his password is not stored in clear text in the database, but as a token.
This token expires after 1 year, or if for the corresponding workflow no new instances have been created for 14 days. If the token has expired all activities are not shown at the dedicated user, but in the tasks of the Workflow's Controllers.

The Controller has to enter the credentials for the unattended-activities-user and afterwards the activities are shown at the dedicated user as expected. Starting with DocuWare 6.8 the behavior has been improved.
The token will be refreshed automatically in the background, so there is no need to enter the credentials manually unless the user's password has been changed.