Samsung LC34F791WQUXEN 34 inch monitor problem

[dog-man]

I have the above monitor and if I set my display at 100 Hz and I turn off the monitor, when I turn it back on I just get a grey or black screen. I cannot see my desktop.

If I set my display to anything below 100 Hz, I don't get this problem.
The monitor is capable of this setting and is advertised as being so. I have read numerous reviews about how good it is at 100 Hz.

So what could be my problem?

I have a high spec computer running the latest win 10, 1080 Ti graphics card.
1000w power supply.
I connect the graphics card to the monitor with HDMI.

Is it a case of needing to use DP for connection rather than HDMI?
I have not tried that yet.

 

[dog-man]

When I say setting the monitor at 100 Hz, I am referring to the refresh rate.
I already have the resolution set to the max capable.

I will try a DP cable when I get home.