Your payment may have been sent to an email address which is not linked to a PayPal account. To check this, login to your PayPal account and click on the payment's "Details" link... the "Payment To" section of the Transaction Details page will indicate whether the email address is linked to a PayPal account.
If the "Payment To" section says the email is unregistered, the seller may have misspelled his PayPal email address in the payments section of the eBay listing or he may have entered an old email address or he may need to confirm his email address.
The seller should login to his PayPal account, click on the "Profile" tab and select the "Email" link in the left hand column to see if his email address is confirmed. If it's not confirmed, he should click on the "Confirm" button to initiate the confirmation process. To check which PayPal email address was used in the eBay listing, the seller should click on the "Sell similar" link for that eBay listing and look in the payments section for the PayPal email address.
If the seller has access to that email address, he should login to his PayPal account and "Add" the email address to his account. The payment will show up right after he confirms the email address.
If the seller does not have access to that email address, you should cancel your payment and ask the seller to send you an invoice (Request Money tab) from his PayPal account so that you can pay to the correct PayPal email address.
~Sandy
