Hi GN,
Try this,
- turn off your device
- detach your Surface type cover
- press and hold the power button for 30secs
- followed by pressing at the same time Volume up+ power button for 15secs
- if you see another windows which is TPM just exit or cancel without saving
- it will reboot your device and once your already on the welcome page(sign in screen) attach your surface keyboard.
- sign in to your device and check if your surface keyboard keys are working
if not call for Support and asked for a replacement.
take note: replacing your surface keyboard will be replace for free if its still under warranty.
to check if its still under warranty or not go to this Website and register your device.
the serial number of your surface keyboard is located near on the metal connector of your keyboard
hope this helps