Incorrect assignment for purchase order &

What causes this issue?

Replenishment element &V1& has not been fully assigned.

System Response

No cost distribution can take place for the appropriate grouping WBS
element.

How to fix this error?

Check the result for replenishment element &V1& in the pegged
requirements display.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.