The LP16 doesn’t see MT songs with MIDI file attached

Hi,
I just wrote to the customer service, but kind of an emergency so I also try here.
I want to create multitrack songs with a MIDI file attached in the uTool editor.
I can perfectly export MT songs and play them in the LP16, but as soon as I want to add a MIDI file (using the uTool editor etc..), the song is not recognised.
If I remove the MIDI file from the USB stick, then the LP16 sees the song without problems. I tried many things, exporting the MIDI at different tempo (120, 100), doesn’t help. I also exported MIDI files with the minimum informations (unchecked all the boxes in my DAW – Cubase), and it doesn’t make any difference.
If anyone has an idea… Looks like people manage to play MIDI files here (more or less synced but that’s another topic).
Then, I thought that maybe I could update the device (I have currently 83956). I downloaded the Cymatic Downloader, plugged the LP 16 to my Mac, and then didn’t know what to do with that. Nothing happens, and if I click on the Cymatic Downloader my Mac says he’s unable to open it. I don’t get it. Also strange, the update is supposed to be 83958, but the Cymatic Downloader that is downloaded when I click on the update is ‘83956’, I don’t get that neither.
If I don’t manage to work MIDI files, then it’s totally useless to me, and I guess I just have to send it back.
Anyway, thanks for your help!