If your Mac doesn’t recognize an external display
If your Mac doesn’t recognize that a separate display is connected, you can try to detect it in System Settings, or try one of the other troubleshooting tips below.
On your Mac, choose Apple menu
in the sidebar. (You may need to scroll down.)Press and hold the Option key to make the Detect Displays button appear in place of the Night Shift button, then click Detect Displays.
If your Mac still doesn’t recognize the attached display, try any of the following:
Unplug the display from your Mac, then plug it back in.
Make sure the cable you are using is securely connected to the correct port.
Make sure you are using the correct cable to connect your display.
Tip: To get more detailed information about the type of video display your Mac supports, check the tech specs for your Mac: Choose Apple menu
Make sure you are using the correct adapter, if needed. See the Apple Support article Adapters for the Thunderbolt 4, Thunderbolt 3, or USB-C port on your Mac.
If you are using a third-party display, check the included documentation to ensure you are connecting the display according to the manufacturer’s guidelines.
