Range Pewermax 155x - how can i fix it ?

The above system will only work if you press constant water. If you have water and heating on 'timed' it does not work, and the green boiler light does not click on. All other lights are on and pressure gauge is below 2 (as it should be I believe). However if you put the water to constant the presssure rises fairly rapidly but 'Lock out' does not happen ... any suggestion would be very helpful, Thanks