It is probably NOT your float switch. First thing I would check is if the main wash motor is getting 120V. After your dishwasher fills with water there is a pause but then main wash motor should turn on. You'll have to remove dishwasher from your cabinet to have access to the main wash motor plug because it's at the back. Use a Volt-Ohm meter to see if main wash motor is getting 120 Volts after dishwasher fills. If it does, main wash motor is bad. If it doesn't get 120 Volts, then electronic control board is bad.
FYI, I change lots and lots of main wash motors and electronic control boards on Whirlpool built dishwashers (KitchenAid, Maytag, Jenn-Air, Amana, etc.).