EBay buyer not responding to case in resolution centre. What to do?

Hi I'm really sorry if this is long winded but I really need some advice. I recently sold an iPhone on eBay that I'd bought off Gumtree but then when I reset it I couldn't get passed the activation screen because of the previous owners details being linked to the phone. I decided to sell it on eBay seeing as I couldn't get in touch with the person I bought it from. I clearly stated that the phone was stuck on activation mode and I wouldn't accept returns. Anyways a person bought it from me and I sent it out right away, a couple of days later the buyer messaged me and said that the phone was completely useless to them. I said I'd be happy to offer them a refund and pointed out that I clearly mentioned that it was stuck in activation mode in the description. The buyer responded saying to please refund them now so that they could send the phone back and opened a case at the same time saying the same thing. I replied saying I'd be happy to refund in full once I received the phone. It's been 5 days since then and I haven't heard anything:|
Where do I go from here? Can I, as a seller, escalate the case or will eBay decide in the buyers favour? If the buyer doesn't respond will the case be closed in my favour?
Any help would be greatly appreciated

The buyer has to send you the phone 1st ( they have to prove that it was sent and received by you ) , ie special delivery or recorded mail. It is ebays policy that they send it back to you before you refund. Do not refund until you have your phone and it is in the same condition that you sent out.
If they do not send back recorded etc, they will lose the case.

Reply to ebay that you have asked the buyer to send back for a full refund.

Seasoned ebayer

I recommend not escalating the case yourself. To do so does make sense to me, and I had a similar nightmare with a difficult buyer who refused to return the item that was claimed to be defective.

The best thing you can do at this point is stay on top of all communications. If the buyer responds through eBay, respond back. Always keep "the ball in their court". Do not communicate with the buyer unless they communicate with you. If they do not return the phone, they do not receive a refund. If they choose to escalate the case to eBay, they will be told by eBay to return the phone.

Keep 2 things in mind. 1st is that they may be trying to scam you (very, very possible). And 2nd, they may have managed to unlock the phone and all is well.