Hi Adrien!
At this point, I think our research so far points on the MIDI settings on your kiwi 3P.
- Are you using the latest firmware version? (from the JX-3P Upgrade, just to be sure we are reading the same manual)
- Have you tried different positions with the external selector switch?
- Are you able to establish connection using any other software (kiwi editor, MIDI Quest 12, etc)
This may seem obvious, but also check the MIDI connections In>Out, Out>In, cables, etc..
By the way, are you using/have you tried this layout? (its was made to program the KIWI-3P from the iPad):
https://mididesigner.com/qa/171/roland-with-organix-and-kiwitechnics-update-mks-jx-8p-mks-70
Ed.