SAP Message R1091 - Grouping & has external number assignment, enter a number

Diagnosis
The business partner needs a key to identify it. This key was notspecified.

System Response
The system issues an error message.

Procedure
Enter a key in the dialog. If it is a background process or an XMLmessage process, contact your system administrator.

1579049FMCA_BRFP: Create BP external numbering