Not a good sign. Is there anything on the ad that says you can not return it? If not, ebay will support a claim against the seller if the product was misrepresented in the ad and would not honor a return request.
They can't do anything about the serial number. It should have been on the box as well, so you could go to FiiO and authenticate it. If the seller said no returns, or you are past a limit of 7 days, etc. you may have to bite this one.
I sold a netbook on ebay and clearly said no returns because you really have no control over what someone may do to a device when they get it. Even then the buyer complained about how it worked, and I sent several emails to try to help him resolve any issues. He started to get nasty so I stopped helping. He never took my advice anyway. LOL.. but most ebay dealings I've had have been flawless. And I've had hundreds.You just have to be very careful and ask
the right questions, and if you are a seller, cover your butt, but be honest about the item up front.
Edited by avaddikt - 6/4/14 at 11:02am