Sorry to hear that. I'll say this, even with an option to re enable it on mine, it disable itself all the time. There is a Promaster forum (general van owner not RV's) that have talk about this issue even with the factory radio. But it usually is an aftermarket radio people have that the blind spot stop working.
Mine will be fine and then I'll not drive it for a couple of weeks, press the brake while driving and then I see the warning about it being disabled.
I would just double check you're not part of that older TSB that Jayco updated the firmware for the Maestro. Other than that, it might a good idea also to take the van to a near by car audio store cause it might be the Pioneer or the Maestro unit itself that isn't working.