Deletion of notification allocation to order & not allowed

What causes this issue?

You tried to delete the assignment of the notification to the order.
This is not allowed, because the notification is assigned to the order
header.

System Response

The system does not delete the assignment.

How to fix this error?

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.