Go to Help and Contact.
In the drop down menu, click on Resolution Centre.
Choose I did not Receive my Item. It's the default.
Enter the required information.
You don't have to contact the seller, though it is polite. If you tried and he ignored you, go to the next step. People get hung up on that all too often.
If the seller cannot prove delivery, and do not voluntarily refund you, Paypal will and then go after him for their money. There will be other fallout for him.
Talking to customer service will only slow down this process.
You only have 45 days from purchase for this. If more time has passed there is another possibility that does not involve eBay.
