Mazda 3 2010 GT. Hot Air ONLY driver's side

I have a 2010 Mazda 3 GT. Went on a long road trip. In the middle of the road trip I noticed I was unable to change the driver's side air conditioning to be hot air. Instead it was freezing cold and nothing I did on the knobs would change that such as adjusting the dual temp knob or putting on the A/C button or not. It was permanently on freezing cold on the driver's side where the passenger side would function proper at any temperature regardless of what I changed. I did some reading on this issue and everyone says its the actuator that controls how open or closed the vent is (Mazda part number BBT1-61-A60). Both the driver's side and passenger side has one so it made sense to replace the drivers side. I took it to my trusted mechanic and he independently came to the same conclusion and replaced it. Unfortunately this hasn't resolved the issue and I'm still unable to change the temperature on the driver's side and my mechanic doesn't know what to do. He wants to replace the knobs but that is an expensive fix and we don't know if thats the issue. I should mention on the dash the screen says it is supposed to be hot air coming out so I don't believe it should be the knobs. Any advice would be greatly appreciated!
Thanks!