ok I think I figured it out.
you have to use an adapter that supports 4k HDMI 2.0
if you try anything else it wont work. I have a an display port to HDMI but it didn't work.
also MSI confirmed to me that using the built in HDMI wont make it work. they managed to get it working by using a USB type C adapter to HDMI.
this is a link from other thread.
I've seen 2 people with black screens get it working with this, might be worth a shot.
https://www.amazon.com/Cable-Matters-DisplayPort-Thunderbolt-Compatible/dp/B00K0UDJFI/ref=sr_1_1?ie=...hope this will help.
am waiting my adapter and will let you know once I receive it.
Omar