WSUS 3.0 SP2 (Win2008R2) downstream replica server "Result unknown" when trying to synchronize with new Upstream WSUS 4.0 (Win2012R2)

We are migrating our WSUS infrastructure based on Windows Server 2008 R2 with WSUS 3.0 SP2 (Version: 3.2.7600.226) to Windows Server 2012 R2 with WSUS 4.0 (Version: 6.3.9600.16384). After deploy the new upstream server with Windows Server 2012 R2, we are facing a problem when trying to synchronize one existing downstream server (Windows Server 2008 R2) with the new upstream server (Windows Server 2012 R2). The result is always "Unknown".

In "WSUS Options" we put in the "Update Source" the port number 8530. Is that correct? Is there an adcional step to do?