Do Paypal first. If the seller doesn't respond, they will refund your money. And if the seller can't come up with a delivery confirmation you'll receive you're money. Stay on Paypal about this. Do not give them an inch.
Also call Paypal after filing online. The last time I called, they immediately recredited my account while I was on the phone. No waiting period.
Then right after you file with Paypal...go to eBay and file against the seller.