Why is the heat and air system only working on emergency heat?
when running the heat-pump the air blowing from the heat ducts
is not hot ( it's to cold for the heat-pump).
you have a main furnace and it won't turn on ( is thermostat
selected for this source), ( is the power switch for main furnace
on ), ( is fuse for this furnace good).
If these are good (check thermostat wiring at thermostat, and
transformer).