Hello Sanifan,
The first thing I would try is to make sure the mini-emptor is completely swung into position. I picked up a G5 in the fall that supposedly was non-running. When I got it home the first thing I did was push the mini-emptor in REALLY hard until it clicked. Sure enough it started right up. You will notice there is a little tab on the mini-emptor that must actuate a small switch on the body of the vacuum in order for it to run.
If you have already tried this, you may have an issue with the switch itself. It is actually located right there underneath the housing next to the mini-emptor. It is an integrated unit, with the receptacle for the power cord, the nozzle/hose speed switch, mini-emptor safety switch and main power switch all in one body. The main power switch gets actuated via a linkage that runs from the rear lever you depress with your toe along the side of the machine. I haven't seen this linkage for sale so much, but the switch unit itself is not hard to find. I'm including a link to one that also includes a diagram of it and some instructions.
The picture is from a G3 I have currently partially disassembled which may give you an idea of the lay of the land. (Sorry I couldn't keep the switch and the rear lever and linkage both in focus).
You probably want to make sure the motor is not seized up completely by making sure the fan spins freely. Also, I think the brushes can get gunked up enough to keep the circuit from completing, but I'm not sure how you diagnose that. Maybe someone else can chime in.
Good luck,
Joe