2009 Passat air pressure checked but light stays on

Hello, That sounds funny. Go by literally any tire shop and tell them the light is on. They will scan each wheel with a wireless scanner to see if they pick up a signal. If there is no signal from one or more, it will not be communicating with the system. The tire pressure sensors are on the back of the valve stems, and they run on battery. If they have never been replaced, the batteries are probably dead. Some places rebuild them, others replace, and you should be looking at around $30-60 per wheel.