- Check cable connection
Ensure the HDMI, DisplayPort, or VGA cable is securely connected to the correct port on the external monitor. - Check USB-C port
If an external monitor doesn’t work via USB-C, it may depend on whether the laptop’s USB-C port and the Thunderbolt 3 adapter are compatible. - Update drivers
Update your graphics driver to ensure you have the most up to date version and check your monitor specifications to ensure the adapter and monitor are compatible. - Change Mode Settings
Check if you need to change the settings on the external monitor and laptop. This could depend on the laptop’s display mode settings. - Check External Monitor Power
Make sure that the external monitor is powered on. This could depend on separate power sources depending on the monitor.