Sounds sort of like you had a refrigerant leak, and the system is low, causing a lockout. This is likely something a service tech might need to look at. If the reverse switch valve is not working, it can't make heat. Don't know enough about a heat pump to help more. Does the thermostat have a setup so it can control a heat pump? Is it hooked up properly? There may be a dip switch or jumper that needs to be moved. Carefully read the installation instructions again and make sure you use the section on a heat pump to verify it is wired properly.