If anyone want to simulate the same behaviour, just close the cylinder valve and start your car... or remove an electrical connection to the main solenoid valve of the CNG kit...
Some how in the morning your CNG kit main solenoid valve does not opens. Could be due to weak solenoid, weak electrical connections to it or low battery volts before cranking. Low battery volts may be due to direct radiator fan or anything that turns on before sulf... or simply weak battery...
This valve of CNG kit opens when we turn the key to ON position before ignition with a tuk sound and if we do not crank, it turn back off with another tuk sound.