My Surface Pro 3 connects with an external Dell monitor well. When the system was running Windows 10 version 1709, I was able to set my secondary monitor as the primary one. After the recent v1803 update applied, I open the Settings app and click on the “make this my main display” box then it becomes grey out. I uninstall the current display adapter in Device Manager and my tablet doesn’t detect it at all. How can I resolve it?
How to fix Main Display Greyed Out and lower resolution in Windows 10 multiple monitors
* First you need to turn both monitors on.
* From your desktop, right-click your mouse and go to Display Settings. You can also open Settings app, go to System > Display.
* On the right side pane, click on the identify option to check the devices.
* From the available screens, select the number 1 or 2 picture of the monitor which has the rectangle around, and it will turn orange.
* Now you are able to access “make this my main display” check box. Finally check the box, uncheck and recheck it to configure your main display.
I also face other problem. The correct resolution of my tablet is 1920×1080, and the external monitor uses 1280×1024. When I use duplicate function to extend the screen, main screen goes to a lower resolution. The related box is greyed out.
When you use the duplicated screens without third party software, both displays have the same resolution and are set to the smaller maximum resolution by default.
You need to use full video device software to fix the issue. I open the NVIDIA control panel and adjust desktop size and position, but it requires a digital connection for the external, either HDMI/DVI/DP, not VGA.