This issue has been fixed if you are using our newest firmware. Make sure you have run the update with the Chubby Buttons app, and you are running "Chubby Buttons 2 (KS)". You can see the advertised name on your list of Bluetooth devices.
If you are running an older firmware, you can toggle the on-screen keyboard by tapping ">>" and "volume up".
Android On-Screen Keyboard Issues:
Here are some best practices to make sure the on-screen keyboard doesn't go missing while using your Chubby Buttons 2: