My 50 cents on how I addressed my issue and for documentation purposes.
I had the same issue with an exception on Event Viewer:
System.Exception: Failed to retrieve document list from the specified QVS
at QMSBackendCore.Service.ServiceImpl.GetUserDocumentList(Guid qvsID)
I noticed that QlikView service properties (in services.msc) has the Log On option to authenticate the user. In my case I was using a domain user that could only be authenticated with network communication on. Once the authentication was able to work the Server got connected. A workaround for this is to have a local user instead of a network/domain one.