First, be sure it is still turned on. It is fairly easy to bump the button to the left. Second, be sure you are going fast enough. The cruise will not work at too low an rpm, so it may kick out or fail to engage at something like 40-45 mph in fifth gear, and at lower speeds in lower gears. It also ill not work if you ride the brake pedal even slightly. The VSS can kick it out, too. Otherwise, serious faults can also disable it, like the a brake or steering failure, but these usually result in fault messages and/or limp mode. The cruise control uses the CANbus (digital network) system, so it is not fused, per se. If it still doesn't work after you check your switch, brake, and speed, it is time to visit your dealer.