Please check the following:
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.
6) Please contact us (ZOWIE website: contact/RMA ) for further assistance if all you've tried all the above.