When I turn on my honeywell thermostat it says its on, but the furnace and the heatpump don't don't turn on. What could the problem be?

Did this problem just start?
Did you check all switches and circuit breakers to make sure they are on.
If you set the thermostat to FAN ON does the fan does the indoor blower come on?

Brand and model number of thermostst and unit?

My crystal ball is broken and I cannot see the brand or model numbers from here anymore until I get it fixed.