Samsung phone screen crashed now won't boot (further details below)

Hi!

Sorry if this has been asked before but I’ve run into a bit of an issue with a Samsung Galaxy S7 Edge, the owner of the phone stated the events that caused this to occur are…

He was browsing the internet with the battery discharging, he left it unlocked and went to check up on his wife when he returned to the phone less than 5 minutes later it had a blank screen with the two touch buttons at the bottom lit.

He let the phone die and I’ve tried to recharge it, via the original cable and charging socket, an alternative cable I know that works same socket and air charger in the car.

When you plug it in to charge it does nothing and the PC does not recognise a device is attached.

I’ve tried charging it for an hour and doing all the button presses (power and volume up as well as power, home and volume up) there is no response at all.

Any advice would be greatly appreciated!

Thanks