Item &1 does not have a delivery-relevant schedule line -> no correlation

What causes this issue?

Item <(>&<)>V1<(>&<)> in the sales order does not have a delivery-
relevant schedule line.

System Response

The system cannot run a delivery group correlation for this item.

How to fix this error?

Either indicate that the item or its schedule line(s) is relevant for
delivery, or ignore this message.

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.