It's hard to advise you wit no information on how the return was arranged.
If you opened a case through eBay's money back guarantee, and the seller provided a prepaid return label, all you need to do is escalate the case for eBay to step in. When returning items, eBay accepts tracking evidence of attempted delivery, and will enforce your refund. If the address on the label was incorrect that's the seller's problem, not yours.
If you haven't opened a money back case, how did you go about arranging the return?
