A/C won't change vent setting?

My A/C won't change its setting. What I mean by that is I slid the lever over to defrost, and then over to defrost/floor, but now it wont blow anywhere except on the window and on the floor. The lever slides freely(almost too freely) back and forth fine, but it won't change where it blows. I can't set it to come out of the vents or just the floorboard. In other words, the lever moves back and forth fine, but the air only blows as if its on the defrost/floor setting no matter where i move the lever. The A/C does blow cold, there is no issue with that.