RIfusion

I bought a 2010 sel and picked it up today. The previous owner had ugly 20" wheels and tires, so the dealer switched them out for me and put on the 18" sports package rims with Eagle 225 45r18 tires. I drove the car about 15 miles and the Tire Pressure sensor now gives an error. Checked the tires and they are all at 36lbs. Any thoughts? thanks.