Can the Gio be used with the USB MIDI Input on the Duet for iPad & Mac?

No. The GiO is a digital audio interface as well as a USB control surface, which means it requires a MIDI driver to be installed on your computer to work correctly. This fact makes it unusable with the Core MIDI Input on the Duet for iPad & Mac.

Workaround: Use a different USB port on the Mac or a USB Hub