If you wish to go ahead with this sale go right of the item sold to More Actions, and select Send payment Details, amend the International postage there to that required, but do not click on reset. Check it is correct, and send .
If you are on the Seller Hub, you click on the item in Orders >> Awaiting Payment, then top left you will see send Invoice, follow the above instructions.
If you do not wish to post this item internationally, go right of the item sold and from More Actions select Cancel this Order selecting the reason Problem with Buyer's Address.
If on the Seller Hub, find the item in your Payments tab >> All transactions. Click on the item's highlighted item number, and far right click on the big blue button from down menu there, select Cancel This Order.