Just left the kid in kinder garden and tried get out of the parking spot, got that msg - hv battery shut off ???
Could not drive away.
Pressed stop than start a couple of times, finnaly decided to lock the car with the remote and unlocked it and that did the trick.
But what the hell ?
I am not 100% sure that you do have a problem.
Why, because I have seen this very same issue before by not following the start up process correctly.
I am NOT saying you don't have a problem, but I have seen this very same warning when doing the following.
Okay, unlock the car and reach inside and hit the "START" button, wait a few seconds, then hit the "START" button again.
Remember, you are standing outside so have NOT pressed the brake pedal.
The car will run through the usual checking process and start bonging.
Straight away you will see the very same 12 Volt amber warning display in the dash panel !.
I think it does this to warn you that power is being drawn from the 12 volt battery and because its knows you are NOT ready to proceed / drive it is therefore inform you that recharging the 12 volt battery is NOT taking place.
How did I discovery this, purely by accident.
I wanted to know how much range I had in the car before I started a trip.
So because the car was NOT on charge, I though I would reach in and hit the start button ( twice ).
I got the information I wanted, but received the 12 Volt warning at the same time.
How could this be related to your problem ?.
Well, could it be possible you hit the "Start" button JUST before you applied enough pressure to the foot brake ?.
If so, you have almost replicated the same condition as myself.
Powering the car down, then leaving the car and locking & unlocking, then returning to the car and carrying out the "START" process correctly this time after the reboot did the job !.
If the 12 Volt battery never had enough power to start the car the first time, I can't see how it found the power the second time.
Unless of course, you had been running the heater for a long time with the car powered down.
This will use power from the 12 volt battery to run the heater blower fan's.
Only when following the proceed to drive process is power supplied to charge the 12 volt battery.
Hope this makes some sense !.