Just tested this on my Android phone, and this problem seems to be the case when running the "web version" from the Mitch app, for me. The keyboard shows up, but it will not type into the input field. (Notably, when the keyboard is displayed, the entire game window shrinks to accommodate it.)
When I install the APK version of the game, it allows me to type and enter a name, correctly. (In this case, the keyboard appears to overlay the game window, rather than shifting its contents.)