Lets try something that usually works for most Xbox One issues. What I am going to have you do is what's called a Hard Reset.
Press and hold the power button on the front of your Xbox One console until it shuts off. Once it is off, unplug the power supply from the back of the console for 30 seconds.
Once the 30 seconds are up, plug the power supply back in to the rear of your Xbox One than turn it back on. Once it has fully booted up and you are on the home screen signed in, attempt to use the on-screen keyboard again.