When Windows cannot detect a second monitor, first check whether the physical connection is normal, including power supply, cable plug-in and interface compatibility, and try to replace the cable or adapter; secondly, update or reinstall the graphics card driver through the Device Manager, and roll back the driver version if necessary; then manually click "Detection" in the display settings to identify the monitor to confirm whether it is correctly identified by the system; finally check whether the monitor input source is switched to the corresponding interface, and confirm whether the graphics card output port connected to the cable is correct. Following the above steps to check in turn, most dual-screen recognition problems can usually be solved.

It is really annoying that Windows cannot detect a second monitor, especially since you have connected the cable, but the system just doesn't respond. This situation is usually not because the monitor is broken, but most likely there is something wrong with the setup, driver or connection method. Don’t worry, the following common reasons and solutions will help you check step by step.

1. Check whether the physical connection is normal

Many times the problem lies in the most basic connection. First, make sure that your second monitor power is on and whether the cable is plugged in. Common interfaces include HDMI, DisplayPort, DVI and VGA, and different interfaces sometimes have compatibility issues.

• Make sure both ends of the cable are tight
• Try changing a wire (especially old wire)
• If you are using an adapter (such as USB-C to HDMI), it may also be a problem with it.

Some laptops require you to manually turn on the external monitor function, usually press Win P to open the projection menu and select "Expand" or "Copy". If you just plug in the line and don't operate this step, the system may not recognize the new device at all.

2. Update or reinstall the graphics card driver

If there is a problem with the graphics card driver, it will also cause Windows to not recognize the second screen. You can update the driver in the following ways:

• Right-click on "Start Menu" and select "Device Manager"
• Expand "Show Adapter", right-click your graphics card model, and select "Update Driver"
• Or go to the official website to download the latest driver installation

If the update still doesn't work, you can try uninstalling the current driver and restarting it, so that the system can be automatically reinstalled.

In addition, sometimes the old version of the driver is more stable. If you have problems with the driver just recently, you can also consider rolling back the version.

3. Manually detect in the display settings

Sometimes the monitor is actually connected, but Windows does not actively recognize it. You can manually check it:

• Press Win I to open settings → System → Display
• Drag to find the "Multiple Monitors" section and click "Detection"

If the system still doesn't respond, you can check whether only one monitor icon is displayed in "Display Settings". If there are two but one of them is grayed out, it means that the monitor is not correctly identified.

Another situation is that the docking station or multi-port monitor adapter is used. Windows may not support certain models. It is recommended to check whether the manufacturer provides driver support.

4. Check whether the monitor itself has input source settings

Some monitors come with multiple input interfaces (such as HDMI1, HDMI2, DP, etc.), but by default, it may not switch to the port you are connected to. For example, if you use an HDMI interface, but the monitor currently chooses DP input, the screen will naturally become black.

At this time, you can press the "Menu" or "Source" button on the monitor to manually switch the input source to see if this is the reason.

If it is a dual graphics card laptop (integrated graphics card independent graphics card), you should also pay attention to which interface you plug in the output cable. Some laptops are output from the integrated graphics, while USB-C is output from the independent graphics, and they may not be recognized even if the insertion is done.

Basically, these are the investigation directions. In most cases, the steps of checking the cable, updating the driver, and manual detection can be done. If it really doesn't work, changing the interface or restarting the system is also worth a try.

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