You need to understand that buyers and account holders are not necessarily one and the same, as accounts can be hacked or otherwise fraudulently used.
Buyers have 180 days from purchase date in which to open a Not As Described or Item Not Received case with PayPal or their card issuer. This is the banking industry norm, as international purchases can take months to arrive. And the only way to win an Item Not Received claim is if you have tracking, or a 16-digit delivery code, which proves delivery to the address on the PayPal payment confirmation email.
Account holders can also open an Unauthorised Account Use claim, as has happened here (lodged because the account holder claims they are not the buyer of your item, ie their account was hacked or otherwise fraudulently used). UAU cases can be opened for up to 13 months because many folk only receive their bank and card statements annually. The only way to win such a claim is by uploading a copy of your Proof of Posting receipt to the claim, as requested. It is the only thing that PayPal and any payment processor will accept for such a claim. If you don't have it, then you will automatically lose the claim, and be charged a hefty admin fee into the bargain. So always keep your POPs for at least 13 months.
If you do have a POP receipt, then upload it now. If it proves dispatch to the address on the PayPal payment confirmation email, the claim will be closed, and PayPal (or whatever payment processor was used) will refund the account holder from their own coffers if necessary, as per their account protection policies. If you shipped to an address that was different to that on the PayPal payment confirmation email, though (one that the buyer gave you after they'd paid, for example), you will lose the claim.
@deb0046
