Take your volt - ohm meter outside ( yes , I know , into the snow ) . Check , very carefully for 240 VAC coming into and out of the heat pump disconnect . Carefully check to see if the 240 VAC makes it into the unit , at the contactor .
Check for loose connections of the line voltage wiring , AFTER you turn off the power .
Still , with the power off , look for the small low voltage wires coming from the house . Check for loose connections . One of these small low voltage wires will be the C - Common 24 VAC wire to one side of the furnace transformer . One will be the Brown or Orange wire going to the reversing valve .
You probably have other low voltage wires , to . Going to out door air temperature sensor or other things .
Try to post a clear / sharp photo of the inside of the heat pump and of the wiring diagram .
These are the things I would start out doing . Hopefully some one will come along that knows more about heat pumps , than I do .
God bless
Wyr