LattePanda M3-7Y30 alpha stop working after software reboot.

Dears My LattePanda M3-7Y30 alpha stop working after software reboot.

 I had used the Panda since months as Homeassistant server. I update the HA software as usual and the Panda stop working... no more led nether red and blue

I try to plug and unplug the power USB-C cable : 

-No leds turn on

I powered the jst 2.0 4P with 12 volts : no led

I takeoff the RTC battery and put in back : no change

is there another test I could do ? 

Is there some touch point to try to identify where is the fault component ?

Thanks for help.