Have you opened a return through Ebay and now have an open case?
If you don't get a proper return address from the seller in the next day or two, contact Ebay, refer them to the case and get them to make the seller provide a proper return label.
Use the link to get a callback:
https://www.ebay.co.uk/help/eua?id=5275&mkevt=1&mkpid
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)