have you tried unplugging the monitor from power source and then plugging back in? alternatively, i read on Linus that a similar issue was resolved by using a newer model display port cable. good luck.
HDMI 2 ports of 18.0 Gbit/s bandwidth is able to handle 1440p 144Hz with a Premium High Speed HDMI Cable but doesn't mean Msi has enabled 144Hz over HDMI with your monitor. To allow HDMI over 60Hz is a manufacturer choice rather than a limitation. To determine if it can look through the manual. Also does your graphics card have HDMI 2 ports? list your pc specs.
Most likely you need a Displayport cable. What cables did the monitor come with?