The problem I ran into was PXE booting (Volume Down + Power) a Surface Pro 3 and found that it brought up the PXE boot IPv4 screen but when I pressed the ENTER key to continue nothing happened. I tried to bring up an On Screen Keyboard (OSD), plugging in an external keyboard, using a dock and using a different keyboard cover but that did not resolve it.
What did fix it was going in the bios (Volume Up + Power), deleting the SECURE BOOT KEYS, rebooting into the BIOS, installing the SECURE BOOT KEYS, rebooting and holding the Volume Up + Power for 15 seconds to reset the system.
I have done this dance several times and I think all you need to do is the so called “hard reset” which is:
Press and hold the Volume UP button then press and hold to Power button for a minimum of 15 seconds. Ignore anything that flashes on the screen or backlights on the keyboard… just keep holding for 15 seconds.
then you can PXE boot again by::
Press and hold the Volume DOWN button then press and hold to Power button for 5 seconds
Let go of the Power button but keep holding the Volume DOWN button until the screen turns on
After that the keyboard worked as I expected on the PXE boot screen.