Why is your air conditioning not working when car is not moving?

Couple things I can think of off the top of my head.. if it does provide cooling when the vehicle is moving, your refrigerant level is probably the issue - perhaps too much of it or too much PAG oil. This causes a low superheat and makes it more difficult for the heat exchange to occur. Bent fins on the condenser which are prohibitive to the passage of air through the fins is another possibility. When you get your car washed, do you put high pressure water directly to the grille? If so, there's a good chance its caused bent fins on your condenser (as well as on the radiator).

The main cause I see is an inoperative radiator/condenser fan.