Datasource cannot be created (August Release)

Hi,

I've installed Power BI Reportserver (August Releasse 15.0.2.557 ) on 2 nodes with software NLB and scale them out. The reportdatabase is placed on a named SQL instance. The SPNs for all nodes and for the virtual name are added to the service account. Kerberos constrained delegation for the SQL instance is added to the same service account. The service account of SQL Server is able dynamically to register its own SPN.  On database level I was able to confirm that the PBIR Service is using Kerberos.

Everything worked fine and I can access the page either via the virtual name of the NLB or via the URL of each node, but I can't create any datasource. I'm getting the error "An error has occured. Somethin went wrong. Please try again later."

I've checked the ReportServicelogXXXXXX.log. The stated error is 

ERROR: [56x1bucj]: OData exception occurred: System.Net.WebException: The request failed with HTTP status 401: Unauthorized. at Microsoft.SqlServer.ReportingServices2010.RSConnection2010.SetConnectionProtocol() at Microsoft.SqlServer.ReportingServices2010.RSConnection2010.SoapMethodWrapper`1.ExecuteMethod(Boolean setConnectionProtocol) at Microsoft.SqlServer.ReportingServices2010.RSConnection2010.SoapMethodWrapper`1.ExecuteMethod() at Microsoft.SqlServer.ReportingServices2010.RSConnection2010.ListExtensions(String extensionType)

Any ideas ?

Best Regards,

Bobi