I have a problem with my gas wall heater when the tenant moved out. The heater will not turn on when I turn the thermostat to a higher temperature level, so I check to see if the pilot light was lit, it was. Then I touch the 2 wires together from the thermostat to the heater, no ignition. What gives? Please Help!

Is the heater powered by 120v. If so is the breaker, fuse and or power switch on to the heater.

Some simple wallheaters have a thermopile that generates the power needed to open the gas valve. Either the thermopile or the gas valve may be bad. See if the gas valve gives a voltage, likely mv. Check for DC voltage equal to it between the wires.