If the address is incomplete it's best to cancel the order with the buyer's agreement, this refunds them and your seller performance is not affected, select Buyer Requests to Cancel.

Ask the buyer to correct their address on their eBay account as you will relist the item for them to buy and pay again once address is corrected.  They need to double check at eBay checkout too, left hand side, before paying,  that the delivery address there is showing correctly.

For the unused Simple Delivery label,  the refund goes back to whoever paid for it,  this way....

• If you selected 'Buyer pays’ when you created the listing, your buyer will automatically be refunded for any Simple Delivery label that isn’t used after 30 days

• If you selected ‘Seller pays’ and offered free postage on your listing, you'll need to fill out the Request a refund for Simple Delivery form for the label that wasn’t used. Make sure to send your request within 14 days of your item selling.

@bruce9431