Why cannot my BenQ monitor display appropriately via a USB-C(Type C) cable?

1. Ensure your laptop's USB-C port supports DisplayPort Alt mode or
    Thunderbolt 3/4.

2. It is recommended to use the BenQ certified USB-C cable, which is attached
    to the BenQ product box 

3. If you prefer to use your own USB-C cable, ensure the purchased cable has
    the following features: power delivery and video/audio/data transfer
    functionality.

    • USB-C male to USB-C male

    • Support DisplayPort 1.2/1.4 display (DP alternative mode)

    • Support 4K resolution (3840x2160)

    • USB-IF certified

    • Support power delivery (You could purchase the corresponding cable
      supports 60W or 100W according to the power supply wattage of the
      monitor)

4. It is recommended to use a USB-C cable to connect the BenQ monitor and
    input source device directly.  NOT suggest using any 3rd party adaptor, USB
    docking, or converter between the monitor and input source device. 

5. When connecting a Mac device, try to plug the USB-C cable into another
    USB-C port of the Mac device. The output signal from the USB-C ports of
    the Mac device might be different. 

6. If the BenQ monitor doesn’t have a USB-C port but has a DisplayPort port, it
    is recommended to use one USB-C to DP cable to connect the BenQ monitor
    and the input source device directly.

7. When plugging in the USB-C cable to the monitor and an input source
    device, press the function keys on the monitor and switch the input source
    to the correct one: USB-C. (Not all BenQ monitors have the signal auto
    switch function.)

8. Try to reset your BenQ monitor
    Pressing the function key > Menu > System > Reset All > Yes 

9. Try upgrading the MacOS version on Mac devices or the graphic card driver
    version on Windows devices.

10. Try to reboot your input source device. 

11. Contact BenQ support for further assistance if the problem can’t be fixed.