I have a 2018 Colorado, and the relearn procedure should be very easy.
Set the TS508 to start learning the sensors, but don't learn them as yet.
On the truck, go to the Tire Pressure Screen and hold the check mark down until it says Tire Learning Active. It should beep once.
Then you go to the Left Front Tire, trigger the TS508... then Right Front, trigger, Right Rear, trigger, and finally left rear. The truck will beep each time and light up the marker light for the corner its waiting for... at the end it should beep twice.