01-09-2020 12:24 PM
That you didn't know is irrelevant. The buyer has received an item which is not as described. That is your responsibility. So tell the buyer to open a return request or case for not-as-described. They will tell you through the opened case or return request what they want - either to return for full refund, or a partial refund and keep the item. You don't have to agree to a partial refund, but if not, you will have to agree to a full refund on return, as per Ebay's Money Back Guarantee (which you agreed to abide by when you registered your account).