http://resolutioncenter.ebay.ca/
Open an Item Not Received Dispute, which is the default setting.
If the seller cannot prove that you have received the item, he is required to refund your payment. If he doesn't Paypal will, and go after him for their money. In addition he gets a black mark on his selling account which may increase his fees, lower his placement in Search, restrict the number and value of items he can list, or even get him kicked right off the site.
Since you have already tried to contact the seller, just go straight to the Claim.