Or go to the credit card you really paid with (Paypal is just a useful mediator) phone the 1-800 customer service number on the back and ask the clerk about a chargeback.
She will need information about transaction numbers, dates, currency, payments, etc.
Not all cards require you to prove return Delivery of the item. Some will accept proof of shipping. Some require neither.
But do go to Paypal first.
And if you don't have your PP account backed by a credit card, add it now. Not only does it give you the extra layer of buyer protection, but your payment is truly instant (from your bank account you are really sending an e-cheque, which must clear before your seller will ship). And you can buy when you want, arranging your budget to cover the cost as necessary.
Another takeaway.
Any mail order purchase will be expensive to return if the transaction goes wrong. Even if it is something that is no one's fault, like a difference of opinion over colour (is it blush pink or baby pink?).
Factor in the possibility of needing to return when considering a purchase by mail.