A/C only blowing outside air temperature

Truck listed above is a 2500. It is having issues with the A/C getting cold. The heater works amazing in it so it’s nice in the winter but when I turn it for the A/C it seems like it’s just blowing the outside air temperature which seems to end up with the inside of the truck being hotter than it is outside. Was just wondering if I could basically get a checklist of stuff to check starting from easiest to hardest so I can narrow it down. It’s been a couple years since the A/C went out and I’ve just dealt with it but I don’t know if I can go another summer with this thing blowing hot air when it’s 105 out. Thanks in advance.