When asking questions it would help so much to tell us when and exactly how you paid.
If you bought it for delivery before Christmas it will be too late now to use eBays money back guarantee. The limit is 30 days from delivery. It will also be too late for PayPal, even if that's how you paid, as their time limit is also 30 days.
Was there a manufacturer's warranty? If so, you may be able to claim but all too often warranties for items bought on eBay prove to be worthless or invalid.
If you paid by credit or debit card you can ask your card issuer whether they can help. There's plenty of information online about buyer protection for card purchases, it may be worth checking your rights before contacting them. Unfortunately almost no-one gives us enough information to offer advice.