At least one delivery note has no unique delivery date

7CAUSE&
You attempted to process an invoice document on the aggregation screen
selecting by delivery notes. For delivery note &V1&, the system cannot
determine a unique delivery date (V2&, &V3&). This can be because:
Several goods receipts were entered on different days for delivery note
&V1&.
When the goods receipt for a different delivery note was entered,
delivery note number &V1& was entered by mistake.
During goods receipt entry, no delivery note numbers have been entered
for a number of deliveries.
The "GR-based IV" indicator was not set in the purchase order for one
or more items.

System Response

For delivery note &V1& the delivery date field was not filled on the
aggregation screen.
This also applies to all other delivery notes for which no unique
delivery date can be determined. No further messages are, however,
issued.

How to fix this error?

Check the invoice items assigned to delivery note &V1& and delete the
items that are wrongly displayed. You may have to change the allocation
criteria for the invoice by replacing the delivery note number &V1& by
the purchase order number and re-checking the invoice.
If you do not enter the delivery note numbers at goods receipt, ignore
this message. In this case it does not make any sense to aggregate data
by delivery note numbers. Use a different aggregation level, such as
purchase order level.
If, in an order item, the "GR-based IV" indicator was not set (by
mistake), you cannot change this in the purchase order. Inform the
relevant person in Purchasing so that the error does not occur again in
future purchase orders.

Error message extract from SAP system. Copyright SAP SE.