According to
MSI Optix G24C4 – Redefine eSports rules | eSports Gaming Monitor | MSI your monitor has (2) HDMI 1.4b ports. According to
HDMI Specification 1.4b, HDMI 1.4b supports up to 120Hz at 1080p, but your monitor's specs page says it will do HDMI: 1920 x 1080 (Up to 144Hz). The problem here is that, while HDMI had the bandwidth to run 1080p @ 144Hz since v1.3, it's not a standard requirement for HDMI to support that mode, so your milage in practice will vary. Here's an interesting read
https://www.reddit.com/r/buildapc/comments/8wyg4e
. How did you determine that the "HDMI port is hard connected to the iGPU"? Is this a laptop with HDMI only and no DP?
You may want to try a different high speed HDMI cable.