Geneway Flame Photometer Ignition Problem

Hi,

WE have newly installed Geneway Flame photometer. Everything is working fine but when we try to ignite the flame by pressing the ignite botton up to 20 seconds, the flame ignites and stays ignited untill we release the ignition botton. We are using natural gas as fuel and with air compressor. Also when the flame ignites, the flame sign on the photometer display appears but as we release the ignition botton, the flame gets OFF. Please advise the possible cause and its solution.

Regards