You need to file a claim with USPS. I'm sure you can do that on their website. If there was delivery confirmation on the package you won't be able to get a refund from the seller anyway if you try opening a case with them on ebay. Once the package is scanned as delivered it's no longer the sellers problem. It's a you and USPS problem.
To claim money from USPS in case of damage you must have insurance at the time sending it. USPS is a business just like other corporations. When factories manufacture something some products will be damaged at the beginning. Such things will happen to post office, too. I hate people leaving packages on my front door when I am not at home. If you complain to ebay they will send another one. Also remember there are many frauds in ebay. They will take your money and then hide from the scene.
There are a couple of possibilities. Either it was taken to the wrong address or it was stolen out of your mail box.
Unless you contacted the post office the same day tracking showed it was delivered there is little chance they can retrace their steps and find it.
Opening a case with eBay/PayPal is useless if tracking shows it was delivered.
Ask UPS where the package was left, if it was left with a person (find out who), a neighbor or what. Sometimes packages are stolen from front porches. Sometimes packages are tossed over the fence, so check your yard.
contact the nearest UPS office and show them your tracking number.
you have to go the office and give the details.
