2013 Chevy Trax cabin air stuck on Vent

Hi everyone. I have a 2013 Chevy Trax with 90,000 KM on it. Recently ran into an issue where cabin air (warm or cold) only comes through the front vent regardless of where the switch is set - e.g. I cannot direct air to defrost or floor. The actuator knob was quite tight for some time and then it loosened up. I can still move the knob to individual settings but air still only blows through the vent. Is this a broken actuation cable and is this something that someone here has maybe fixed before and has some step by step instructions on diagnosing the problem and repairing it? I'm willing to take the dash apart.

Much appreciated!

Earle