You have 45 days to open an unreceived item claim in PayPal. If the 45 days have passe since the order was placed, then there is nothing that can be done at this point. Did you leave negative feedback for the seller, because if you can still leave feedback, I recommend you do asap.
If the 45 days have passed you can go to the credit card you really paid with (Paypal is just a mediator) and phone the 1-800 customer service on your card or on your credit card bill. Ask the customer service clerk about a chargeback.
Have all your transaction numbers, dates, payment amounts etc. handy to help the clerk process your refund.
