Go to the Resolution Centre at the bottom of this page and open an Item Not Received dispute.
The first suggestion is that you contact the seller. If you have already tried this, go on to Escalate the Dispute to a Claim.
If the seller cannot prove delivery (not shipping, delivery) you will be refunded.
Do NOT accept an offer of a replacement. It will not arrive.
Do NOT believe that a refund depends on closing the Claim.
A seller can refund within seconds once she sees the Claim.
Do NOT close the Claim until you see the money in your Paypal or credit card account.
If you are too late for the eBay dispute, go to Paypal and follow the same steps.
PP hides its Resolution Centre at the top of the page under Tools.
And in future, if it sounds too good to be true, it probably is.