Adjust the gas regulator and water regulator to meet your desired temperature. To increase temperature as high as possible; turn the gas regulator control from LO to HI and turn the water regulator control from HI to LO.
Check source water temperature. If the source water temperature is too cold then you may need to ‘cycle’ the water through the system back into the source reservoir then through the appliance again to meet your desired temperature.
Check if there is a flame in the ‘viewing window’. If you cannot see a flame it could mean that the unit has switched off / not ignited, try restarting the unit and monitor the 'viewing window' for a flame.