The Buyer has 30 days from Delivery to open an Item Not Received(INR) dispute.
You win if you put the tracking number in the dispute showing Delivery. Not shipping, delivery.
You must do this yourself, eBay wants you to actively participate.
No tracking? Refund promptly to avoid getting a defect.
If it has been over 30 days, your buyer likely opened a chargeback with their credit card.
Much more serious.
Respond as above. If you can show delivery, eBay has your back.
If not, refund immediately.
If eBay has to step in, they will charge you $20 for refunding the original payment, and give you that Defect.
