Reject Outbound Delivery - Sales order could not be delivered

Hi experts,

I tried to reject a outbound delivery in EWM.

Easy to do - Open /SCWM/PRDO, process code at item line, O001, create Outbound Delivery.

Working fine, delivery in ERP was adjusted to qty 0 --> great.

Now i want to deliver again...open the order (VA02), press the deliver button...BUT I can't deilver as the overall status is "Completed" (in VBUK).

What am I doing wrong?

Thanks

Michael