why can't create Return Shipment No. Series

when I create a Purchase Credit Memo,then run test report,there is a warning message,that is, Warning!Return Shipment No. Series must be entered I enter Ctrl+F8,and it shows Return Shipment No. Series is blank. And I insert a new credit memo again, it succeed. It is so strange. Why? p.s. I am sure that the Series No. have been setup.

Hi, Have you assigned the Posted Return No. Series after creating the Purchase Credit Notes?If yes then you have to reselect the Buy-from Vendor No. on Purchase Credit Memo Header Card.