Hi, first thing to check is whether it's just jammed, then move onto whether the motor is turning and whether the linkage is still intact.
I'm afraid it's likely to be a strip down job to diagnose the problem. I'll help you where I can but it's not going to be local as I'm in Reading. However with the power of smartphones, I'm sure you can take pictures and/or video so I can help.
Joker Smoker will also probably be able to help you, he can strip down and rebuild a Traeger, blindfolded, in 22.6 seconds - so I've heard
