Following are the steps for troubleshooting laptop not displaying images or videos on external monitors:

1. Check whether the laptop is connected properly to the monitor.
2. Check and confirm that the laptop supports the resolution of the monitor.
3. Disable the secondary display connected to the laptop and reconnect again.
4. Update the display driver of the laptop.
5. Roll back to a previous version of the display driver.
6. Back up all important data of the laptop and perform a full system reset.