If your display is black or doesn’t work as expected.

• Check the cables and connection.

• Make sure the display is connected to power (if it requires a power source) and that it’s turned on (if it has a power button). If you’re not sure if your display requires power or has a power button, check the documentation that came with your display.

• Make sure that your Mac supports the display. See the Apple Support article If your external display is dark or low resolution.