Why can’t I set the frequency to 240Hz on my monitor?

Please check the following solution :

  1. Make sure to use an HDMI 2.0 or DP 1.2a cable.
  2. If an HDMI 2.0 cable is used, make sure to connect to the correct HDMI 2.0 port.
  3. If a DP 1.2a cable is used, make sure to use the one bundled by BenQ.
  4. Make sure to update to the latest graphics card driver version.
  5. Make sure that your graphics card supports 240Hz.
ESD Refresh Rate 240Hz