- Check to see if the external display is properly connected.
- Check the video cables to make sure they are securely connected.
- Restart the computer.
- Reboot the compuer.
- Adjust the resolution and refresh rate.
- Check the video driver.
- Reinstall the video driver.
- Uninstall and re-install the driver.
- Check for updates.
- Seek help from the manufacturer or certified technician.