from documentation i have from robertshaw on millivolt gas valves you should have a minimum of 325mv from the thermopile with nothing connected to it. basically hold the pilot knob and test it out of the circuit. if this is good then you should have 200mv with the thermopile hooked up to the gas valve and the main burner on. if the main gas valve does not ignite or you have less than the dropout mv when trying to fire, the valve coil might be bad or there is resistance somewhere in the circuit not allowing the generated voltage to open the valve. the valves i have used has a cut out around 100 to 120 mv.
Is what you get when you didn't get what you wanted.
A positive attidude will not solve all your problems, but it will annoy enough people to make it worthwhile.