Buyer gives incorrect address and then won’t communicate

I sold a card and shipped it via eBay Standard Envelope. Almost a week later it is returned to sender, “not deliverable as addressed”. I’ve mailed many, many cards this way and never had this issue but I know sometimes USPS can be weird about them so I chalk it up to that. I figure I’ll just print a new label and try again but I double check with the buyer that the address was correct and even sent a picture of the original label. They’re only reply was “the address is insert different address” to which I tell them that is indeed a different address and they will need to update it within their eBay settings before we proceed. No response for a couple days and I send a follow up reiterating what they will need to do. It has now been a couple days since then and I still haven’t heard anything. I plan on following up one more time and then giving them another day or two before I call the whole thing a wash, refund and relist.

But I have a few questions:

1. If they update their address will I be able to print a new label with the updated information without having to refund/relist/repurchase? Or will the address provided to me always be the one that was listed at the point of the transaction?

2. If I don’t hear anything and I do cancel/refund I will definitely get a strike on my account right? I’m not that worried about it, stuff like this very rarely happens to me but it would be nice to know where I stand.

Thanks!