This week there were Surface Pro 4 firmware updates as part of the Patch Tuesday updates. After the system updates completed on my SP4, the type cover stopped working. The backlight didn’t work and the Surface didn’t recognise the keyboard being removed or plugged back in.
After reaching out to people here at Microsoft, I learned that you can make some internal systems within the Surface reset by holding down the power button and volume up button at the same time for about 20 seconds. That reset got my keyboard working again.
I’ve seen a few forum posts where other people ran into this issue but no clear message about how to fix it, so hopefully if you run into the issue then you’ll find your way to this post with a solution.