The second monitor is not recognized: check if the cable is OK
First, check if the cable you used to connect the monitor to the computer is working properly. Connect the display and PC with a different wire if you have a spare. If the monitor is now working, the first cable may have been defective.
On the other hand, if the screen is still not working, the problem is likely with your computer’s video input or incorrect system settings.
The computer does not find the second monitor: inactive or faulty video connector
If the second display has different ports, check if you can connect it via HDMI, for example, rather than VGA. Many computers also have multiple video connectors: VGA, DVI, HDMI, and Displayport are the most common. Test all ports for which you have the appropriate cables.
In addition, computers often have multiple connectors of the same type. For example, if you connected a second monitor via VGA, chances are there is another VGA port on your PC. Connect the wire to the alternate connector and check if the monitor is recognized.
If you now see an image, it is possible that your integrated video card is disabled, so you are simply displaying the image on the monitor using an additional video card.
How to activate an unrecognized monitor through system settings
Another possible cause of problems is that you have disconnected the monitor from your computer in system preferences. To reconnect it, follow these steps:
- Right click on the desktop and select “Screen Resolution”.
- As soon as your computer receives a signal from the monitor, you will see it on the display.
- Click on the icon of a disabled monitor and select the “Maximize this display” menu item.