Glo KOBO GLO N613 blocked

Hello

I am a happy user of a Kobo Glo..... so far :)
FCC ID: NOIKBN613
IC: 8857A-KBN613
MODEL: N613

Here is the description of the malfunction I am experiencing.

1) I tried to power up my device with the ON/OFF button despite the "connect to power source" message was visible (device initially in sleep mode).

2) The device went directly to a "Reinitialisation phase"

3) Since then, my device is reacting as following:
- Reset actuation (bottom hole): LED is flashing successively Green/blue/green/OFF then the screen blinks with no image/character display..... and nothing more.
- ON/OFF button: when the device reacts, it is as described above

4) What I tried:
- Reset button actuation
- Combinaison of Reset&ON/OFF buttons
- Disconnect battery for hours then connect it again
- Plug the device to power source (to PC and to a wall outlet): sometimes the LED goes Green, sometimes not. Sometimes the LED goes green when I remove the power plug ....
- Change the SD card keeping the same root image.

I am now stucked and I fear that the hardware is OOO.
The only thing I can try is load a new image maybe....

What is you opinion ?

Thanks in advance

Sorry for grammar and spelling slaughter. English is not my native language.