MBot 3D GRID II+ stopped working: Power Supply pb? Motherboard pb?

Some weeks ago, my MBot 3D GRID II+ stopped working. When I turn it on the LCD screen flashes a white display for a fraction of second then nothing.

I presume the problem comes from the mother board or from the power supply.
But I don’t have more clues…

Did anyone experience the same issue?
How can I figure out what is wrong?

Thanks a lot for your all help!