if he has it listed as working you cant blame him for the shipping damage. If you do end up going that route, I hope you dont rip him off and file a claim and end up keeping the A4000 and the refund. (its happened to me before..theres losers as sellers and buyers)
Do what others have posted to see if its something that needs to be reseated. I hope you know what you're doing and dont screw it up more. (I've had that happen to me also)
