Try with a DP connection and see if you still get the issue.
Around 3 months ago I bought this monitor and it worked fine. But when I tried to enable 143.98Hz the screen kept on going black randomly for a few seconds. Luckily, this has stopped. But when I try to enable 239.76Hz (the highest refresh rate the monitor can do) the monitor just goes completely black, but it is still turned on. When I turn it back to 143.98Hz on my second monitor, the AW2720HFA goes back to normal. This is really annoying, so does anyone know how to fix this?
AW2720HFA, 239.76Hz highest rate, goes black