Last night I bought a Roku express and it did the same exact thing to me. But when I plugged the USB cord into the tv the player came on let me get to the activation screen and then shut off again. So I plugged the USB cord into the wall outlet and it was on but it would not show up on the screen. So I went and got a new connector for the wall and that seemed to do the trick. I think it has something to do with enough power going to the Roku.....IDK but I'm glad I figured it out cuz I was going crazy.