waveshare 10.1" hdmi display : no sound

Hello,
I have installed latest DietPI for Odroid C2 , and it works neatly, but I cannot get the sound on a Waveshare 10.1" touch display (resolution: 1024x600) to work.
When I connect the Odroid C2 to a HDMI TV, the picture works and “aplay” plays a wav file correctly.
When I unplug the HDMI cable and plug it to the Waveshare 10.1" touch screen, the picture is displayed correctly, but the Waveshare display somehow never plays the sound (and yes, I checked the display menu - sound volume is suppsedly at 100%).

Do you have any kind advice for me how to get the HDMI sound to work on this Waveshare touch screen ?
Do I need special boot parameters, etc. or is it a hardware issue ?

OH SHIT, it was a faulty and brand-new hardware.
I’m sorry!