If you have the hot and common wires connected (black to black and white to white) it should work. If not, try connecting a length of wire to the ground wire and connect to ground, such as a copper cold water pipe, radiator, heater vent, or the ground terminal in a nearby outlet. If it works then, you need to splice an extension to the ground wire to connect in the box where the hot and common are. Keep in mind all splices must be inside an approved box. If it still doesn't work, yours is not the first nor the last defective hood to be sold.