Was the GR of the inbound delivery made from VL32N, or was it made with MIGO?
If you had not received with VL32N then you cannot cancel it with VL09.
But even it was received with VL32N it is not easy to narrow it down, since there are 215 OSS notes for VL09 and inbound delivery.
Especially if no reaction is coming, which I consider as error, then there is almost no starting point except having it debugged by an ABAPer to see what SAP checks where it get lost.
Maybe the status in the delivery is not as it should be to allow a reversal, double check with note 1972280 - Incorrect status for inbound delivery that is not relevant for goods movements