GMC Canyon guy

I had this exact same issue with my 2019 Canyon. I left the Canyon parked in Storage for 3 years, but did not disconnect the battery as I was running it from time to time just to get things moving. Eventually the battery depleted too far, and the truck would not start. So I put a trickle charger on it and got the battery fully powered back-up, however, the back-up sensor stopped working as a result, causing the exact same conditions, and by exact, I mean exact same 100% conditions as described above. I replaced the battery with a new battery as the original one now no longer would hold the charge at all. I just recently took my Canyon into the GM Dealership, describing all the conditions, and mentioning this Forum with this posting and that I have the exact same issue experienced. They did not simply take me for my word as to what the solution could be, instead they of course did their normal 1 hour diagnosis to find the problem, discovered that the Master Module controller (not sure what it is called) locked up, and needed to be completely reset (which only the GM Dealership can do). Once they reset it, and hooked the battery back up, everything functions as per original settings, parking assist problem went away and works fine now. I was told to never leave the battery connected when storing a newer type vehicle for an extended period of time as the result is the battery will get depleted too far, and will cause the 2nd battery in the Master Module to also deplete too far, causing the module to stay locked, and the only way to unlock it is to have it diagnosed at a GM dealership and get it unlocked and reset. This was a $190 lesson for me.