I am sorry but this is what ebay does if sellers don't accept "not as described" returns.   You can appeal the decision if you think it was wrong - here:

https://www.ebay.co.uk/help/selling/managing-returns-refunds/appeal-outcome-case-seller?id=4369

And you can  still ask the buyer to return the item.   If they agree you can buy return postage online and send them the link or QR code for it.