The Paypal Resolution Centre is at the top of your account page under Tools.
The first suggestion is to contact the seller, since you can't and it is only a suggestion, immediately escalate to a Claim.
Tell PP that the seller is Not A Registered User (NARU). This shows where you have your feedback number behind his name.
This will speed up your refund.
You have up to 180 days after payment to open a PP claim, but do it immediately.
If the seller was new, or only sold occasionally, or was already marked as questionable by eBay, he doesn't have your money.
EBay has a 21 day HOLD on payments made to sellers in those categories.