Here are some troubleshooting steps that may help.
- After connecting the monitor in your laptop press the Windows key + P at the same time and select between Extended or Duplicate display then press Enter.
- If it will still not work, do uninstall/reinstall the graphics driver.
- Go to Device Manager and uninstall the graphics driver.
- Next is to open Programs and Features then uninstall anything related to the graphics card.
- Once uninstalled, download and install the latest driver.
- Reboot the laptop once the latest driver has been installed then test it again.