Did you ever get this figured out? When I got my truck a 2014, the cruise worked intermittently. But one time it wouldn't work for a long time and I replace the brake switch but that didn't help. So I slapped the top of the cross bar just above the switch and that has worked every time that it won't come on by itself.
I have never checked my AlfaOBD to see what it says about the cruise. But the slapping works.