Proof of delivery for delivery & already verified

What causes this issue?

The goods movement for the delivery cannot be reversed because a proof
of delivery (POD) already exists.

System Response

You can only reverse goods movement if there is no POD (either quantity
verification or confirmation).

How to fix this error?

In this case, it is not possible to reverse the goods movement. Create
a returns delivery instead.

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.