Check this exit as well.
IWOC0002 PM/SM notification: Check whether status change is allowed
From exit documentation:
Furthermore, the customer exit enables field checks to be made in the current notification and allows the status change dependent on the inspection result.
If the required value is not available, I think, it will restrict the status change to Notification Completed.
With QQMA0014 QM/PM/SM: Checks before saving a notification, check the status of notification & you can address your requirement.