It's been very cold lately. I have my thermostat set at 70 and my heat pump runs non stop but does not get to 70 degrees. Stays around 63 -64 degrees. Outside pump is icy .

Outside heat pumps do form ice and will defrost at specific times as programed on the defrost circuit board. If your thermostat is set at 70 degrees and your home is not 70 then it is possible your aux heaters are not working,the heat pump has met its maximum output for outdoor temperature conditions, or you need to call for on site service to find out why.

Shut off the thermostat. Wait about 5 minutes. Now turn on the blower fan to "on" not "Auto". Let it run for about 2-3 hrs. (Change the filter before doing this). Turn on the unit with Fan on auto and everything as you run usually a/c on. If it does not work, try the earlier step for a longer time like 4-5 hrs. and turn the unit on.