Please follow the troubleshooting methods to proceed：
Check whether the display plug connection is normal.
Check whether the monitor power button is on.
Check whether the monitor is correctly attached to the port.
Note: When using the discrete graphics card which the video graphics are not providing from the integrated CPU graphics, the embedded motherboard video port will be disable. Please attach the display cable to the graphics card directly.
Check whether the computer is contacted to third-party vendor equipment. If yes, please remove it then restart up the computer.
Check whether the user upgraded hardware by himself, for example memory, SSD, wireless network card etc. If yes, please remove updated hardware and install original hardware to test again, then Check whether the error disappears.