With the GiOConfig application installed you can determine whether the buttons on the GiO are transmitting data. Double-click  and open GiOconfig from the Mac’s Applications folder. Under the Expression pedal curve setting you’ll see a Value: and grey rectangular bar. When pressing a button on the GiO the rectangular bar should turn blue and a Value of 127 displayed. This would indicate that GiO is transmitting MIDI data to the Mac and can be checked with all the buttons of the GiO.

GiOConfig button check

http://www.apogeedigital.com/support/gio