DocuWare Services and Application Pools do not start after the service/application pool user has been changed.
The reason is that the DocuWare Services and Application Pools use Microsoft Message Queueing (MSMQ) to communicate since DocuWare Version 6.6. At the very first start the "private message queues" are created. These queues are bound to the service / Application Pool user. If the user changes the queues are not accessible anymore, so they fail to start.
That behavior will be solved if you reset the Microsoft Message Queue. Please follow this aricle to reset the MSMQ: How do I reset the Microsoft Message Queueing (MSMQ)?