Steamdeck powering on but no display on built-in screen or external

Hello,

When I try to turn on my steamdeck, there is no image displayed on the built-in screen or on my television. I use official valve dock.

I have the 3 short notes when I turn it on and the led is on when I plug it with official power adapter.

I tried the 3 seconds power button hold, the 10 seconds and the OS boot holding volume up + power button. No success, no image.

Any idea?

I'm in France and for the moment I don't see any other option than bringing it to a repair center but I don't know the procedure or where to find one...

Thanks in advance