Message SAP WTADDI257 - & is not a valid vendor for requesting additionals via BAPI

Diagnosis Vendor &V1& has attempted to request an additionals IDoc for anadditionals document via BAPI. This vendor is not allowed to use thisfunction. System Response The additionals IDoc is not generated. Procedure First check your entries. If you are still sure that you have entered the correct vendor, you canmake the necessary changes to the additionals vendor directly in theadditionals monitor. Then you can start the BAPI call again.