I live in Virginia. The temp is around 45F. I have Ducane heat pump outside. it is not running at all but the inside furnace fan is working well. I just changed the defrost circuit board since the HVAC service guy said the old one needed to be replaced. The thermostat seems in good condition because i just got a new Honeywell 5-1-1 programming one and works well. So far, the defrost circuit board and thermostat are all brand new. What is the problem to cause the heat pump not running? I pressed the valve button on the heat pump which can make it run. But it stops if i release the press. Is there possible to be the circuit board wiring problem?

Any advice is appreciated. it is so cold here.