I figured this out a while ago, and have shared it with people in game when they were having issues.

Problems with the chatbox being opposite of the keyboard?

Simply press the back button to bring up your keyboard. Then press, and hold, the back button until the chatbox stops cycling. You may have to press, and hold, the back button twice to get them back in sync.

Thanks, I've had this issue myself and had to restart the app completely.