I open again this topic

I have a MK2N N°3444 with a blank screen
It is an uniform blank screen which turn off after few minutes
I tried to hard reset it with a magnet : the screen was blinking but stay blank
It is readable from OSTCtools
I could not upgrade it from 2.21 to 2.7 with bootloader v1 but I did it successfully with bootloader V2
So now it got a 2.7 firmware
Any magic procedure ?
Regards,
Xavier