These things are cheap. Maybe not as cheap as you <g> but they are made with the least expensive components that will meet their requirements. If Midway does not replace the tumbler or take it in for repair, you can do this yourself. If the problem is nothing more than a loose wire, you can systematically determine which wire you wiggled to make the motor run again.
There is also the possibility that the bearings are shot. When you turn the motor on and it doesn't spin, is it totally silent or does it hum? If it hums, the bearings are likely shot. If you take a drill with no bit in it and close the chuck all the way you might get the motor started by pressing the tip of the chuck into the center of the bolt holding the counterweight in. My cheap Harbor Freight vibratory tumbler has served me well for 6 years but a couple of years ago the motor would not start on it's own. I've used this technique to get it started and it still runs for its 3 hour cycle several times a week once it gets started.
If the motor is completely dead, you can replace it with a bathroom exhaust fan motor if you are really cheap and don't want to buy a new tumbler and if you have more time and skill than money. You may save $20-$40 by doing this. Most people don't have the time or want to bother so they simply buy a new tumbler.