Dude, HDMI 2.1 supports 120hz full 4:4:4 10 bit bandwidth. it sounds like your graphics card has only HDMI 2.0 ports which only do 4k 60hz 4:4:4 at 8 bit or 4:2:2 at 10 bit. I would recomend either replacing your graphics card, or using a display port 1.4 (assuming your graphics car supports it. it should but check anyway.) to a hdmi 2.1 adapter. also make sure that your port isnt being used in a legacy mode or whatnot.