Clearing the Windows 10 external monitor cache

I bought a Surface Book on day 1 of its availability, 2 years ago this month. It’s been an excellent machine. I almost never use it with the clipboard undocked so I’m not sure I’d buy another one, but it’s been good.

Recently, though, it has developed a displeasing habit of failing to recognize external monitors. For example, last week when I was at Ignite, I had to borrow Richard’s laptop to do my product demos because mine wouldn’t talk to the monitor we had available. When I got back from Ignite, it was worse– I couldn’t use an external monitor either through the Surface Dock or the built-in DisplayPort. It didn’t matter what monitor or adapter I used, either. The only way I could make an external display light up was to undock the clipboard and plug the dock connector into it.

I tried a large variety of things to fix it, including updating the firmware on the Surface Dock, reverting to an older preview build of Windows, sacrificing a chicken, and loud cursing. Nothing.

Then I posted on Reddit. Within an hour or so, a user posted a link to this thread, and I found the magic solution. I unplugged the dock, deleted HKLM\System\CurrentControlSet\Control\GraphicsDrivers\Connectivity and HKLM\System\CurrentControlSet\Control\GraphicsDrivers\Configuration, plugged the dock  back in, and boom! The external monitor now works normally.

My theory is that a bug in Windows 10 and/or the Surface dGPU driver and/or Windows Insider upgrades caused the problem. I’m not really interested in figuring out the root cause now that I know how to fix it.

Hopefully this will help future generations who may have this same issue…

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