Impossible de démarrer normalement, longueur de noyau invalide

Hello,

I have this message that appears this morning on my J6.
could not do normal boot invalid kernel length

I can't restart my phone in download mode to download Odin.
I admit I've looked for tutorials but they don't work. I've tried pressing both side buttons at the same time and nothing happens.

Can you help me?
Thank you
Charlene