[mothered]

nike just replied saying
“We have double-checked our courier's GPS

It doesn't conclude that the driver left the package as Indicated by their GPS coordinates.

and have checked the delivery address

As per above.

and weight of the parcel

The weight has no relevance to nonreceipt of goods.

They should know better.

Thus, we regret to inform you that we are unable to refund the item due to the facts we have gathered.”

For the said reasons above, their facts do not solidify their decision to decline the claim.

Will appealing matter and mentioning the DPD situation?

Yes, request an escalation.