Front Wheels Not Turning ?.

First step is to see if there is any crap in the gears that is preventing them from turning.  While you can't turn the wheels very far, you should be able to wiggle them back and forth a bit.  If they're frozen solid, I'd be looking for something like ballast in the gears.

If an external inspection doesn't do it, you'll have to pop the shell and see if there's a detached wire on the motor.  At that point, I'd turn the flywheel enough turns in each direction for a full drive wheel rotation to see if anything's binding.