Help, Engine Won't Start!
 

2014 MCS A/T 65,000 miles

Wify came home from work last night (25-mile commute) and we tried to restart the engine about 5 minutes after shutting it off to go out for dinner. But it would not even crank/turn over at all. It just made a very unusual clanking sound just once whenever the "START" button was pressed. It wasn't the typical "clicking" sound from starter solenoid when battery is low. I checked the battery voltage and it wasn't low at all at 12.6 as expected. I tried to jump start anyway using my truck, but still no start just one "clanking" sound. It almost seemed like the engine got hydrolocked by fuel or coolant.
Here is a history of our MCS.
> We are the original owner and wife drives it 95% of time.
> Never like this happened in the past.
> Never had an accident.
> Never had any engine related repair.
> Car drove perfectly all its life.
> Drivetrain Error "maximum output not available" message has been popping up on the screen quite regularly for last few months. But not affecting performance and no unusual driving symptom.
> Been changing oil/filter religiously every 7500 miles.
> Serviced air filter & ATF fluid about 5000 miles ago.

Can someone point me to the right direction and advise what to try before I call a tow truck?
Only thing I can think of trying is to remove spark plugs (original) and try cranking the engine, to rule out the hydrolocking.

Please help and your input will be greatly appreciated.
Thanks.

My condolences. Anything new to report?

If automatic, is the trans set to Park.