With the cockpit cover on and the support poles in place,no water should get in. Is the boat left in the water? If so,I would suspect something else,leaking boot or something. And Formula bilge pumps are not the sensor type you describe,they have a mechanical float,will not come on unless the float is tripped. If the pump doesn't come on with the manual switch you have a problem with wiring,breaker,switch, or pump itself. Time for a little electrical detective work.should be somewhat easy to find. Good luck