On the H9 side, my recommendation is to set each H9 to its own MIDI channel. Using H9 Control app, go to Pedal tab > MIDI Settings > MIDI Receive channel > set it to 1 for H9-A and 2 for H9-B.

On the Airstep side, the default is set to send program changes for each of the buttons. Pressing them should at least change the presets on the first H9. Does that happen?