O:Please try the followings:
1. First of all, check if the monitor cable (HDMI/DisplayPort) is connected properly to both the monitor and the motherboard or notebook.
2. Please try other monitor cables.
3. Monitor settings

-Press the icon above to select the specific monitor input that you are using, e.g. HDMI.
-Try another monitor input.

Other troubleshooting
-Test the monitor with another motherboard or notebook to check if the monitor is working.
- Please try the output of the other GPUs, as you might have multiple GPUs in your system. (One or more PCIe graphics cards and/or integrated graphics)
4. Check Power cord connection.