Members are supposed to keep their contact information current.
Paypal allows clients to have several addresses on their accounts. Why? Well, at one time the additional addresses were called 'gift' addresses. Handy at Christmas, eh?
Selllers are required to ship to the Paypal address. The eBay address may not match and is not required to (see 'gift' addresses) But it is sensible for a seller to ask his buyer why the addresses do not match. Sometimes it's an oversight and the buyer is happy with notice of a potential problem.
It is now reported as missing. What are the rules about this?
Did you use tracking/Confirmation of Delivery? If so, give the number to Paypal when asked.
If you can see that the item is delivered give the date of delivery to help out the PP customer service clerk.
If the item shows as still in transit, you have some respite when you give the tracking number.
Did you ship overseas by Surface? With or without tracking, you may as well refund right now and avoid black marks on your selling account. Ask the buyer to refund the refund when the item arrives in a couple of months. Never send Surface overseas again.
Did you ship without tracking? Refund. Unless you can show delivery (not shipping, delivery) the buyer wins the case. Again, ask the buyer to refund when the item arrives.
Most people are honest, if impatient.
Not every transaction will be successful.
