Reset iPad keyboard

Press and hold the 'keyboard' button bottom right of the keyboard, and after a second or two you should get a popup - tap Dock on that and it should move back to the bottom of the screen

This only works if my keyboard is not split. How do I dock my split keyboard?

This didn't work in my case. The function is not responding. What else can be done to reset the keyboard to its original position?

What 'function' is not responding ? If you don't want to use split or undocked keyboard then Settings > General > Keyboard > Split Keyboard 'off' should move the keyboard back to the bottom of the screen

The function of "Press and hold the 'keyboard' button bottom right of the keyboard, and after a second or two you should get a popup - tap Dock on that and it should move back to the bottom of the screen" is not working. However, when I set the split keyboard to 'off' that moved the keyboard back to the bottom of the screen. I have no idea what I did yesterday that moved the keyboard to the centre of my screen. Any ideas?

If split keyboard is enabled in Settings then the pressing and holding of the keyboard button should work. As to what you did yesterday, I don't know