wrote in message

It's not entirely that it doesn't work - if I turn the heat off via
the thermostat and then back on I can hear the unit start up, but no
air, hot or cold, comes out of the vents, then after a few minutes it
shuts down.

At two years, is it still under warranty? If so, you know what to do.

The heater is coming on, but the blower is not. It may be something as
simple as the belt from motor to blower is broken. It may be the motor is
not working, it could also be a relay or some other control. Check to see
if you can turn the motor by hand.