No heat on drivers feet
Is there heat anywhere else?
HVAC systems tend to default to defrost mode when a fault occurs for safety reasons. (The way you worded your problem leads me to believe you have heated air going elsewhere.)
A failed actuator for the mode selector is a possibility, or maybe the control panel is bad. Sometimes there is a re-calibration procedure for the system. One of the experts here will probably know if that’s the case. Does the car have automatic climate control?