Hi,
Do try to uninstall/reinstall the graphics card driver that may do the trick.
- Go to Device Manager and uninstall the graphics card driver.
- Check Programs and Features as well and uninstall anything related to the graphics card.
- Once uninstalled, download and install the latest driver from the manufacturers site.
- Reboot your laptop once the latest driver has been installed.
- After the reboot do try your external monitor again, press the Windows key + P at the same time and select between Extended or Duplicate display.