Base UoM of shipment is not = purchase order item quantity schedule.

What causes this issue?

The base unit of measure in the quantity schedule of the purchase order
item is different from the shipment.
The base units of measure must be the same.

System Response

The system does not accept the assignment of this purchase order item.

How to fix this error?

Please use another purchase order item.

Error message extract from SAP system. Copyright SAP SE.