Does the power button on the front beside the LED screen illuminate white? After the rear power switch on the back is flipped on, the front power button will turn on and then after pressing the front power button the screen will turn on. If that's not happing call Traeger, you may need a controller.
Try switching on and off slowly, a few times. Sometimes the DC power module goes intermittent. If the controller power butter does not illuminate, probably a bad power supply brick. It's under the pellet hopper.