Coming back from an errand I tried using the cruise control according to the owners manual and it didn't come on.
The next day it wouldn't work either so I happened to hold down the MODE button on the steering wheel for a few seconds and then got a "cruise control deactivated" message. Then it would work.
I didn't read in the owners manual where this would occur.

 

Do your brake lights work?
Has it been scanned for fault codes?

 

I scanned for fault codes and nothing.
Didn't check the brake lights.