Cannot use internal display and external display at once

[bristolexile]

Hi - first post please go easy. Would anyone have any idea why....

Three identical Surface Laptop 2 devices (identical Win 10 Build) one by one we plug into a USB-C to HDMI adapter over HDMI cable to wall mounted display, two of them display to external display (and internal) perfectly whilst the third will only display internally - nothing at all on the external display. Then I press "Win + P" and select "Select second display" and immediately the internal display turns off but the image is displayed perfectly on the external display! We have changed adapters and HDMI cables with no success.

To me this proves that the transmission path is fine - it works fine on two machines. Are there any settings that could cause this? Maybe power to the USB-C port perhaps? The content wasn't 4k it was just the home screen.

Thanks in anticipation,

 

[jnjroach]

Hi - first post please go easy. Would anyone have any idea why....

Three identical Surface Laptop 2 devices (identical Win 10 Build) one by one we plug into a USB-C to HDMI adapter over HDMI cable to wall mounted display, two of them display to external display (and internal) perfectly whilst the third will only display internally - nothing at all on the external display. Then I press "Win + P" and select "Select second display" and immediately the internal display turns off but the image is displayed perfectly on the external display! We have changed adapters and HDMI cables with no success.

To me this proves that the transmission path is fine - it works fine on two machines. Are there any settings that could cause this? Maybe power to the USB-C port perhaps? The content wasn't 4k it was just the home screen.

Thanks in anticipation,

Any pending updates (Firmware, Hardware Updates, etc.) on the device that is misbehaving? Honestly for most issues, I do a factory reset it tends to be quicker.