A/C vents

That description is very familiar. The cable assembly that goes to the mode selector has either broken or the top of the cable where it attaches to the door cam has come off. Depending on which end is the issue will make it easier or harder.
The control head is screwed to the back of the trim panel in the middle of the dash. It just snaps in place. With it out the control cables are visible as image 1 shows.
The other end of the cable control is mounted on the left side (driver) above the gas pedal on the HVAC case. If you remove the trim panel over the drivers side foot-well you should be able to see the controls. (pictures 2 and 3) Moving the knobs moves the cables.
The usual problem is the clips that hold the cables breaks and the controls move but the actual control doors do not. Then it depends on what failed. If it is the outer part it can be replaced and everything works. If it is the inner door the heater assembly and dash need to come out to replace the bad parts.