Assuming that it is a 36v cart with vglide, Put your multimeter on the 2 small terminals of the solenoid...With the key on in forward and go pedal pressed you should see battery pack voltage...If you do and solenoid doesn't click replace it...If you don't have pack voltage at the terminals your problem is elsewhere (key switch, microswitch)...Follow this thread for a color wiring diagram for your cart ( thanks to CTD)
http://www.buggiesgonewild.com/elect...on-switch.html