Since you only have 45 days from purchase to start a refund claim for undelivered merchandise, take a close look at the calendar and if you are actually under that deadline, go to Customer Support up there on the top right and click on Resolution Centre.
If the seller is unable to prove that you have recieved the item (and sometimes a family member forgets to mention arrival, it happens) you will be refunded by PP who will then go after the seller for the money. There is other fallout for the seller.
You can also leave appropriate feedback for 60 days.
If more than 45 days have passed, go to the 1-800 customer service number on the back of the credit card you actually paid from. (Paypal is just the processor, keeping your financial information confidential among other services.) Cards have longer deadlines, but do not delay because they do have deadlines.
The CS rep will need, dates, prices and transaction numbers, so have those handy to help her get your money back.
