1. Check if the external display is properly connected to the computer.
2. Restart the computer and external display.
3. Update the display driver to the latest version.
4. Make sure the power cable to the external display is securely connected.
5. Reset the display’s refresh rate.
6. Try connecting your external monitor to a different port.
7. Test the hardware with another monitor.
8. Roll back the software update that caused the display issues.