Ac blower is working, unit outside works, but we are not getting any heat, what are the ossible problems

Heat pump, yes? Could be any number of things. Probably going to need a tech to check it out. However, air to air heatpumps really only work to a certain temp. If its really cold outside, they just don't put out much heat, that's when your backup heatsource (be it gas or electric should kick in, or you may have to manually switch the thermostat to emergency heat). Just the nature of the beast.