Hello and welcome to JustAnswer!
There are actually two doors and two actuators that control airflow direction, so it's possible to still have floor and defrost working and not vents working due to a door or actuator.
The problem could be a bad actuator, stuck door, vacuum leak or pinched line in the dash, bad programmer or bad control head on the dash. The programmer is what actually controls vacuum to the actuators.
What you can do is remove the lines at the programmer and try moving the doors with a vacuum pump. If you can move the doors with a handheld pump then you know the doors, lines and actuators are ok, but if not then you know the problem is in the dash.
If you're able to move the doors with a vacuum pump then either the programmer or control head is bad.