Yep, if you have LED bulbs installed without load resisters, this will kill the cruise.
Change the two rear taillight/brakelight bulbs if they are old. You may have a filiment on on of the brakelight bulbs that's burnt. The cruise "triggers" on the voltage drop of the brake lights when the pedal is applied. When the brakes are off, and you are cruising above 35 MPH, the cruise will activate.
Check the overhead cab brake light as well. Is that an LED replacement?
"Never argue with an idiot; they'll only drag you down to their level, then beat you with experience"
2007 F150 STX Supercab (4.6 2V V8), Edge tuner, factory navigation, Mark VIII electric fan conversion with flex-o-lite controller.