cruise control not working

I'm fairly sure that is a drive-by-wire car, meaning there is no linkage from the gas pedal to the motor, the pedal is just a sensor, and the throttle is controlled by a small motor built into the intake. That being the case.... The cruise is just a function of the computer, so here is a quick flow of what could be wrong. Are there any check engine lights or warnings on? Some vehicles will not allow certain functions to be used if there is an error present. Do the cruise control buttons actually function? If they don't the computer will never get cruise commands. Do the brake lights work? Are they stuck on? The reason I ask is because on top of the brake pedal there are two switches, one for the actual brake lights, and one for the cruise, they could both be built into one unit as well. If the switch, or switches fail the car will not turn the cruise function on. Give those items a check before taking it to a shop, because whatever the fix is, it will not be cheap. But it might be easy! The brake switch/s would be my first suspect if there are no check engine lights or warnings.