Hello Nurul,
Shipment Process can be done before of after PGI provided Route is mentioned in Outbound Delivery.
But in your case if the Route is missing in Delivery, then it will not be possible to create Shipment documents. You will have to reverse the Invoice & PGI (Delivery) & determine the Route again.
Also it will be a good idea to keep Route as mandatory in Sales Order / Delivery doucment.
Thanks,
Jignesh Mehta