I'm not familiar with that model but if it is like most newer tractors it might have safety switches for the PTO(s), the brake and the seat and one that detects that the transmission is in neutral if it has a manual transmission. Most will not try to start if the PTO is engaged or if the brake is off or if there is no weight in the seat or if the transmission isn't in neutral, but most of those wouldn't shut the tractor off after it was already running. Did you hit a bump right when it shut down on you" That might have shifted your weight on the seat and cause the seat switch to shift out of position or to fail, or the bump might have caused some other electrical connection to become disconnected.

Please clearly enunciate 'will not turn over'. Do you mean the engine spins when you turn the key but will not fire, or that nothing happens at all.
There's been some confusion on this in the past, so I ask...

My knee jerk reaction would be to check out that seat switch. ***-U-Me(ing) “won’t turn over” means won’t crank, the seat switch could be solely responsible for both the no crank and the mystery shut down condition. I’m not sure either, but that model could be hard wired not to crank without a butt in that seat. Sometimes the no-butt-in-seat no crank can be overridden by setting the parking brake.

dead battery?... because the charger wasn't working for a while and finally the in-tank electric fuel pump drained it?....

in reality there are a million things that can cause a tractor to stop and not turn over... from seizing the engine from lack of oil, to dead battery, to safety switches to operator error (trying to start in-gear instead of in-neutral)...
you'll have to give us more info so we don't just shoot in the dark...