If there is an error in the graphic card, the screen goes blank when an external monitor is connected.
➔ Delete the graphic card driver from the Device Manager and [restart] the PC.
Try this
1. Execute [Device Manager (M)] by clicking the right mouse button on the [ Start] icon from the taskbar on the desktop or pressing [Windows + X] keys on the keyboard.
2. From [ Device Manager], double-click the [ Display adapter] item.
3. Click the right mouse button on the [ Intel(R) UHD Graphics xxx] display adaptor and select [Uninstall device].
※The graphics device name may vary by model. (Intel UHD, Intel HD, etc.)
4. Do not put a check mark on the [Delete the driver software for this device] item and click the [Delete] button.
5. After [restarting] the PC, connect an external monitor and see if the screen is displayed.
6. If the screen is not displayed on the external monitor, check [Delete the driver software for this device], restart the PC, and then reinstall the graphics driver.
This guide was created for all models, so the images or content may be different from your product.