Headrush VX5 won't respond to FC-3

Hello, we are trying to get a Doremidi FC3 pedal to control a Headrush autotune VX5 pedal via USB

We can get the FC3 to do program changes on a Nord keyboard, and the Headrush to receive program changes from a computer - but unfortunately nothing happens - FC3 to the Headrush.

Do you have any suggestions?

The host light on the FC3 is on.

The Headrush webpage says it is USB Class Compliant MIDI

James