No video output for Hikey970

Hello, can anyone help me for this problem?
I have recently tried un Hikey970 board avec une debian 9 version. because its video output could not wake up after une hibenate, I tried to changer le desktop frome LXDI to GNOME but the installation was failed. Depuis that moment, the HDMI semble blocked and don’t show any signal. I have retried to flash back to ASOP, to Debian ou Ubuntu image, always the same resultat: no video output with HDMI. With debian Image, I can always use SSH to communicate aved the Hikey970. Can any one help me or give me some indice to this problem.
Think you very mach.

@blois.hikey you can try using the tool on this link to generate an Ubuntu 18 image and see if that helps

think you very mach. I will try it.