If it's an old email address you can still access, you can add it to your PayPal account to release the funds into it (you can add up to 8 payment addresses).
If you cannot access it, you'll need to contact your buyers and ask them to log into their PayPal accounts and use the 'cancel' button that should be next to the transaction.
Then you can send your buyer(s) a PayPal invoice from your account, ticking it as being for 'goods'. Put the ebay listing title and number in the message text field, just for reference. This will ensure that you're invoicing from a live PayPal payment address.
Let your buyers know that they still have Paypal Buyer Protection paying this route (some get worried that you're trying to circumvent ebay).
When listing again, always check the pre-filled payments address as it can default to an old or incorrect address out of the blue.
