Dreamcast + mClassic doesn't work on my monitor

[Crowzer]

Hello !

I'm looking for help or at least information. I play my Dreamcast with Kaico HDMI adapter and it works as intended on my monitor. But once I put the mClassic, the monitor goes black and sometimes the image show for a ½ second.

The thing is that I don't understand why my PS1 with Pound + mCLassic works fine on my monitor but not Dreamcast Kaico + mCLassic. This combination worked fine on my 1440p monitor, on my previous 4K monitor only the image and on my current monitor... black screen.

My monitor is a Samsung Odyssey Neo G7. I tried on my TV (LG C1) and it works.
Also tried different HDMI cables but no success.

Any idea ?