i had sold something internationally on eBay, it was actually going to israel,
after about a month- month and half, the guy was like where is my package, I said "i don't know check with your post office, it was sent and it should be there"
turns out almost 3 months later the package came back to me still sealed, with a note on it(in hebrew) "nobody picked it up, so they sent it back"
check the items, items where fine, resold the items,
refunded the guy the $$$,-minus shipping
told him to have a good day and that was it
I would tell him to wait, just explain it takes longer to get overseas., meanwhile contact your shipping supplier and se if they can come up with anything