SAP Message VY036 - Marking for release of the item cancelled

Diagnosis
Account assignment for the shipment cost item has been deleted.
The shipment cost item had already been marked for settlement, however.

System Response
The selection for forwarding and the purchase order items determinedare canceled.
The shipment cost item is not forwarded.

Procedure
After you have recreated account assignment for the shipment cost item,you can mark it for forwarding again.