Hi, guys, did you send your issue to Arturia's support? It's like the 1st thing, which I recommend to do.
Anw, the main suspect in this case is the cable/adapter or bad settings, afaik.
You can test it with standard audio Y cable (1x stereo 3,5mm to 2x mono 6,3mm):
- unplug all cables from MF, then check if MF's MIDI out is enabled in MIDI submenu (output dest, arp/seq midi out, knob send ccs)
- plug Y's cable 3,5mm jack to MF's MIDI out and R 6,3mm jack to your soundcard's audio in (with gain set to 0dB) - leave L unplugged and avoid to touch it with anything metal, there's DC voltage on tip
- launch any wave editor (better with visualisation - my fav is Goldwave
) or DAW
- assign proper audio input to new track, launch record
- play any key/sequence/arp, or just turn any knob on MF
- you could see digital signal represented by pulses on recorded waveform then
Hope it helps