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The pressure switch is the redundant back up that prevents the heater circuit from activating when there isnt sufficient water flow.It sounds like the pressure switch has failed-- possibly in the 'closed' postion,... since the tub will not reset, the board in the Gecko control pack 'knows' something is wrong thereby deactivating the heater circuit.To test, you can use a digital multimeter to check for continuity with the spa 'off'. If you get a circuit through the pressure switch- the part is defective.