Just a half baked idea but have you checked to see if the shift indicator might be off or the brake light switch bad. Both can cancel cruise if it is engaged and if they are malfunctioning, may be keeping cruise from engaging.
Might also want to check the cruise fuse.
Ooops I just actually read your post. I would check the brake pedal to find the switch it is many times just a mechanical switch activated by pushing the pedal.
I don't have a Sportscoach so pictures of my rig won't help.
Gary, Cindy, Reacher (Maine Coon), and Vivian (in spirit only now).
Retired: July 31st, 2013 and loving it.
2011 Coachmen Encounter 37 TZ pulling a 2012 Wrangler Unlimited Sahara. Many upgrades, additions, mods, and changes.