Import crm organization to CRM 2015 / ssrs 401

Hi,

I'm trying to import a crm 2013 organization to CRM 2015.

but i can't figure out with the following message:

Setup failed to validate specified Reporting Services Report Server 2015.xxxxx.com/reportserver_sql2015. Error: Error occurred while finding an item on the report server.
The request failed with HTTP status 401: Unauthorized.

The report server is hosted on a separate server than th db server.

I can reach the url that is unauthorized from my laptop or even from the ssrs in local.

In the eventviewer , I get the following entries:

Web service request FindItems to Report Server 2015.xxxxx.com/.../ReportService2005.asmx failed. Error: The request failed with HTTP status 401: Unauthorized.

and

Web service request FindItems to Report Server 2015.xxxxx.com/.../ReportService2005.asmx failed. Error: The request failed with HTTP status 401: Unauthorized.

I had similar configuration for a 2013 CRM environment without the mentioned problem. :(

Do you have an idea???

Thanks in advance,

shoera