Well Seller, there might be 2 reasons as to why this has been occurred.
1. The buyer must be bluffing with an intension of cheating.
2. The item must really have not being delivered by the post to the buyer yet.
This happened to me when I bought a ring through eBay. The tracking was updated as as delivered but I did not receive it. But I waited a little more days without complaining or anything because I keep faith in the sellers. Finally it was delivered to me by the post after 5-6 days.
The best thing for you to do is gently ask the buyer to wait patiently for 5-6 days as their posts really take their time in delivering. But if its the first reason, I hope there's nothing much actually do other than explaining it to the eBay with proof and see where it ends.
Have a nice day
