"No details for medium PRN in Vendor Master Record"

Hi Masters,

We are building SRM7 SP07 with ECS.

1. Vendor is replicated from ECC with no red message in SLG1

2. Vendor belongs to one ECC-mapped Purch Org

3. Vendor has a output medium defined for this Purch Org

4. Purchaser has a default printer defined in Org Structure and in SU01

But each time we create a PO from scratch we get the red message : No details for medium PRN in Vendor Master Record and we have to manually select the printer in the output subtab...

What do we need in addition? WF issue?

Many thanks in advance.