I tried this on my KORG Volca Bass and had the same result. Apparently KORG sets one of the pins differently and the Altura does not like that. Hmmm. Who knows? I tried the Altura on several other MIDI-enabled synths (Dave Smith, Arturia, Roland, etc) and had no trouble… it appears to be unique to the Volcas. I’m wondering if you could change a setting on either the Altura or the Volca (not that there’s many settings on the Volca to change) and get it to work.