Delivery cost addition after GR

Hi Friends,

In the PO, I Had forgotten to add freight charge. I did the GR. I cancelled the GR and now trying to enter the Freight charge. But system throws error that Delivery costs cant be added once GR has been done. But I have already cancelled the GR. Now the PO has no GR document. But still system does not allow me to add freight charges.

Please advice.

Thanks & Regards

Satya