The regulator, gas valve and ignitor can all be tested with common tools that every service technician should have E.g. , multimeter and manometer. Questions that should be asked. Do you have ~ 11.0 to 13.0 inches WC propane pressure at the inlet of the gas valve? Do you have 24 VAC at the gas valve when the heater is calling for heat? Is the gas valve opening when you have 24 VAC applied? Does the propane supply pressure drop too low when the gas valve opens? Can't understand the techs inability to isolate either regulator or ignitor as the source of the problem as the ignitor can be checked by reading ohms of resistance and supply voltage on a call for heat and the regulator can be checked with a manometer??? When checking the gas valve outlet pressure to the gas manifold, instructions in the heater manual should be closely followed as this is a negative pressure gas valve coupled with a "combustion" blower rather than a positive pressure gas valve coupled with "draft inducer" blower.