If no airbrush paint comes out of the gun, the nozzle may be clogged because it has not been cleaned properly. Then you can try cleaning it again with a suitable cleaner. Do not use force to do this, as this could damage the gun. If you are not able to do this yourself, contact a specialist or the manufacturer of the airbrush gun if necessary. If this is not the case, check all connections and make sure that enough compressed air is expelled from the nozzle.