2018 Trailhawk, Same issue
I purchased my 2018 Compass Trailhawk on the 17th of February. The next day took it on a drive through town (50 degree day, btw), and stopped at a store. When I got back using the passive entry, it said something about a break-in attempt, but there was no one else in the lot to have tried. I used the fob to unlock and re-lock the car, and it wouldn't start by the push button. I tried locking the car via the fob again sitting inside, and then unlocking it, and again started the car. This was re-tried 2-3 times before the car started. Upon starting the (A!) Stop/Start message appeared as well. I drove it home, and parked it, being late on a Sunday my dealer was closed. The error cleared the next morning, and my dealer seemed to think it had something to do with the length I'd pressed the ignition button, but had no explanation for the error, but if it cleared, it shouldn't be an issue.
I had no further issues until this morning, when I Auto-started my car, because it was 20 or just under out. When I went to get in, the (A!) symbol was back again when I pressed the button to turn on the car from auto-start mode. I turned off the car, waited a few moments, and started it again. The error was still present, but the car operated normally. I then drove across town (7-10 miles) to work, parked, and turned off the car. I waited a few moments and attempted to start it again. All of my electronics turned on, but the engine didn't even click. I "turned off" the car, and tried again to manually start the car, and got the same results. After turning it off again, I got out, locked it, and attempted the Auto-start feature. The car acted normal, flashing the lights and honking the horn once, but it never started.
I got my dealer to give me a tow, and comparable 'loaner' while I wait, but I'm not feeling very good about my prospects for reliability reading others trouble with similar issues...