Diagnosis
If you're not hearing any motor noise at all from the auger during startup, the issue is usually electrical—either a bad connection, a tripped thermal fuse, or a failed auger motor.
How to Fix It
First, check the simple stuff. Unplug the grill, then open the control box (a few screws on the back of the hopper). Look for any obviously disconnected wires, especially the two spade connectors going to the auger motor. Reseat them firmly. Also, visually check the little cylindrical thermal fuse on the wiring harness; if it's blown, it'll have to be replaced.
If That Didn't Work
The auger motor itself might be seized. You can try to manually turn the auger by reaching into the empty hopper with a long screwdriver—but if it's truly stuck, forcing it can break things. More likely, the motor is dead and needs replacement.
Heads Up
Never, ever stick your hand into the hopper or auger tube to clear a jam while the grill is plugged in. People have lost fingers. Always unplug first.