Climate control mode actuator will not switch?

My air conditioning only comes out of the defroster and far left and right vents, and the feet blower, no matter what mode it is set on. I cannot do the diagnostic test as i have an aftermarket android head unit, however i don’t believe that is the issue because the modes worked before with the new head unit. i’ve seen a lot on here about actuators and what not but i’m just not sure what my problem is, and it’s hard for me to understand. A/C works, and blows cold on both sides, i just cannot change the direction of air, which is frustrating in the summer because blowing cold air at the hot windshield makes it hard for the car to cool down in direct sunlight. anyone have any information or tips i’d greatly appreciate it. just moved to Florida from Chicago so i desperately need my car to stay cool especially with summer around the corner, and i’m not a fan of taking it to the dealer with their outrageous prices. if the solution is just replacing a part i feel adequate enough to do it myself.

thanks!!