Your monitor is stuck at 60 Hz

Windows often starts a new monitor at 60 Hz, even when it can do 144, 165 or 240. Games then can't show more than 60 frames a second however fast your PC is. It takes two minutes to fix.

Set the right refresh rate

1. Right-click the desktop → Display settings.
2. Two screens? Click the one you game on at the top.
3. Advanced display → Choose a refresh rate → pick the highest number.

The highest number is still 60?

1. Desktop PC: is the cable in the graphics card? The ports higher up on the back belong to the motherboard. Use the ones lower down, in the horizontal row.
2. The cable: old HDMI cables top out at 60 Hz at 1440p and 4K. Use the DisplayPort cable that came with the monitor, or an HDMI 2.0/2.1 cable.
3. The monitor's menu: some monitors ship with "overclock" or "DisplayPort 1.2" switched off.

Or let the hamster check

Frame Hamster's free scan checks every screen, and on desktops whether the cable is plugged into the motherboard. Pro sets the best refresh rate in one click (with an Undo).