If the cable is damaged or malfunctioning, Windows wont detect the second monitor. Connect another working monitor to check if the issue is with the graphics card. You may need to update the firmware of the display youre setting up as a second monitor to fix any compatibility issues or bugs.
How do I enable 2 monitors?
Dual Screen Setup for Desktop Computer MonitorsRight-click on your desktop and select Display. From the display, select the monitor you wish to be your main display.Check the box that says Make this my main display. The other monitor will automatically become the secondary display.When finished, click [Apply].
Why is my dual monitor not working?
Verify the correct input: Monitors with multiple input options need you to manually select which cable or HDMI port youre using, like HDMI 1, HDMI 2, DisplayPort, and so on. Change the graphics port: If youre using a dedicated graphics card with multiple output ports, try switching to another port.