Lenovo ThinkPad Display Problems

I'm troubleshooting a Lenovo L460. The problem is that the laptop's display is black when in Windows. I can see the startup splash screen, UEFI, and the laptop's firmware diagnostic screen. In fact, the computer passes those on-board diagnostics.

The weird thing is that as soon as it tries to launch Windows, then the screen goes dark. I don't hear the expected sounds, so I don't think Windows is running. What's really weird is that this occurs whether I'm using the installed version of Windows 10 Pro or a WinPE netboot. As long as it's the lowlevel info is presenting stuff to the screen (like connecting to the server for netboot) I can see the whole display. As soon as Windows launches, black.

The screen dims when I turnoff the computer, so I think the backlight is still running while in Windows.