Remove the service panel cover from the heat pump.
Use your meter to check for 220 volts incoming power to the contactor.(No power check breakers/fuses).
Look at the capacitor,is it bulged on top?(bad).
With refrigerant gauges check for system pressure.(Approximately 120 lbs while idle).
With meter check for 24 volts at common (C) and R on the defrost board thermostat connections.
With T-stat set for heat check common and Y for 24 volts at the defrost board..