Air condition is not blowing through front air vents. No matter what setting the air conditioner is set on, the fan blows through all of the vents except those in the front.

You're as correct as you need to be on the situation. These blend doors/flaps that cover the openings of air flow, are all vacuum actuated and you have a problem with the actuator motors that open and close said doors. It could possibly be the switch/valve itself malfunctioning also.

The most probable cause is that the louwers that should open to allow air in that area is jammed shut. If electronic could be a bad motor, if mechanical cable, bay be gunked up. Do the lever complete its full length of travel or is it resisting and have to be forced?..

You have broken vent flap servos or just need calibration with Volvo diagnostic tool.

Check the duct work under dash might be unhooked

replace the cabin air filters

I've have never heard of a "only cold air system", but hey, nothing surprises me anymore. try replacing the control unit in the front. hopefully that will take care of the problem. If not you need to check your blend valve. (headache depending on location)

you cant adjust it ,this requires the dealers computer to re set it,or a phyiscal control has packed up like a vacumn pipe has split where it pushes onto the valve that controls the flap in the heater unit.

Are the conditions reproduced using the heat side of the controls. If so it indicates possible bad temp controls.

Does the air blow from the defrost no matter what position you set it at? Vacuum leak.

I think it is going to be a vaccum leak.