With the AC turned on,lift the hood and see if the AC compressor clutch is engaged with the engine running.If it's engaged look in the window of the receiver-dryer for bubbles(it's in your cab manual)which indicate low refridgerent level.If the clutch is not engaged,most likely the system is too low to work,indicating a leak for sure with a 2 year old tractor.Newer systems lose very little if any gas.If your system is empty,you could get one of those charging kits to charge it back up,or even add R134a gas with leak detector dye to help find the leak.Proper AC repair for a leak down situation would be repair the leak,evacuate the system with a vacuum pump,and recharge.Keep us posted and good luck!
I do have the WSM for the cab if you need more info.