The heat pump defrost cycle has not begun. This can be a sensing board, refrigerant, or electric heat problem. There is no short-term solution.
You can try to switch it from heating to cooling once every five minutes for a few times to see if the reversing valve will operate. If the outside unit switches in a whoosh and the unit starts to cool, the heat of the house will melt some ice; but the house will be cool. Switching it back to heat successfully would show that the refrigerant components are ok and the problem is related to the defrost board. Switching to emergency heat and successfully feeling heat would show the heater elements are working. Some folks have shut the unit off, put the outside unit under a tent and blew a salamander heater's air inside til the ice melted - a drastic defrost cycle.