The cruise control will not engage if the brake pedal sensor is not made. There's a switch that checks if you brake pedal if fully up. If the pedal is not up, or the sensor bracket is bent away slightly, then it won't make contact and your brake lights will be on.
Turn on your car, put the handbrake on and take a look at the brake lights to see if they're on. If they are, then it's the probably the switch.
Try pulling the pedal up or bending the bracket into place.