"Make sure tires are at the proper pressure. See “Inflating Your Tires” in this chapter. After inflating your tires to the manufacturer’s recommended pressure as shown on the tire label (located on the edge of driver’s door or the B-Pillar), the vehicle must be driven for at least two minutes over 20 mph (32 km/h) before the light turns off."
Did you check the spare? Oh and with mine missing due to my winters tires/wheels it takes about a 30-40 minute drive for the light to come on. Since I start the car in the morning and my wheels/tires are in the shed 15 feet away it picks them up on first start. So you may need to drive a bit.