Sorry, I am aware that grounds are usually connected. But the diagram which Adafruit provided (and which I sent you a link to), did not show any such connection. Since both grounds are present on the controller board, I presumed they were connected internally. Maybe not. I'll try connecting them externally.
And again, the Adafruit diagram should suffice for a schematic - the same link will also lead you to a diagram of the board's internals if you're interested.