No water is going across my humidifier pad. What could cause this?

Before attempting any self-service power down your humidifier. Check your water supply line for cracks or obstructions (you may have to turn off you water supply to the humidifier if you disconnect the water supply hose for inspection). Check your water distribution tray and distribution tray nozzle and clean them if needed. Turn your humidifier water supply and power back on and increase your humidification setpoint via your control. If you still get no water to the tray you may have to involve a contractor.