DIAGNOSIS You're either using the wrong cable type (HDMI 1.4 instead of HDMI 2.0/DisplayPort) or the high refresh rate isn't enabled in both Windows AND the monitor's own settings.
FIX First, confirm your cable. You need an HDMI 2.0 cable or a DisplayPort cable for 144Hz at 1080p. Then, press the monitor's menu button, go to 'Display' > 'Refresh Rate' and set it to '144Hz' there. Now, in Windows Settings > System > Display > Advanced display, the 144Hz option should appear.
IF THAT DIDN'T WORK Update your graphics driver. For NVIDIA, use GeForce Experience; for AMD, use Adrenalin Software. An old driver may not report the monitor's capabilities correctly.
HEADS UP If you're using a laptop docking station or an older GPU, the port may not support HDMI 2.0 bandwidth. Connect directly to a capable port on the PC or GPU.