Was this delivery sent out and then deleted? We have seen this error in the past if a delivery was deleted.
Yes, You are right.
How can i fix this?
Once it is deleted there isn't a way to 'un-delete' it. If there is an issue with a delivery, the best practice is to pause it, and determine if the issue can be addressed. If not, then stop or cancel the delivery. That will mark all recipient delivery statuses as canceled in the system. Once it is cancelled you can create a new one. In this case it would need to be recreated. Let me know if you have any additional questions.