It takes up to 10 days for a payment from a bank account to clear the US and Canadian banking systems. Your seller cannot print a PP shipping label until then.
When the payment clears, he still has 7 days to ship, although most will ship the same day or the next business day.
A credit card backed PP payment is truly instant.....
BUT
New sellers, sellers in some high value/high fraud categories, and sellers with poor customer service may not have your payment released for up to 21 days, pending your reciept of the goods.
Some sellers don't understand this and try not to ship until they actually have the payment.
Is the seller telling you that he has not received payment although you have paid? Did you use a credit card to back your Paypal payment?
If so, explain to him that he can print the PP shipping label and the cost will be taken from your payment, even though PP is holding the rest of the payment pending your reciept of the product.
Let us know his reaction and the listing number.