I had the same issue. Finally found the fix. Open Device and Printers. Turn on your Bluetooth keyboard and click connect to make it discoverable. Next click Add Device on the tablet and the Keyboard should show up. Click it and it'll ask for a passcode. Beneath that box it says something along the lines of you may need a passcode. Click that and it'll generate a new code. Input that code on your Bluetooth Keyboard and hit Enter. Windows will register it and you're good to go.