I don't see how they put it on the seller - they received the package from him and that's the end of that part. It's their global shipping program which they charged you money for (the seller didn't get any of that money) where things went wrong, so it's between ebay, their shipper and you. The shipper says delivered, you say it wasn't, so ebay has to decide who they're going to side with. If they side with you they'll be losing money this time, potentially retaining you as a customer, if they put the loss on you, you will be very very unhappy with them and likely never use that program.
Paypal is now separate company from ebay, so you may want to check into opening dispute with them.
If it were me I'd try to find a way to reach ebay on the phone, failing that go to my credit card company and file a chargeback there. If you win that case ebay will take the loss unless they can offload it to the shipper.