My ac is blowing cold on the right side, but hot on the left side. on 2004 Toyota 4Runner

A tech at the Toyota dealership told me that it might be low on refrigerant. I put a can of refrigerant in it, but it still wont blow cold on drivers side

Asked by for the 2004 Toyota 4Runner
Its the blend door sticking or blend door motor. Can you hear it move when you turn the knob?