Faders 21 and above do not work [done]

[support]

We got your interface, and we checked it.
It was containing the QC (Quality Control) firmware, instead of the final firmware.
The QC firmware is uploaded into the interfaces during the mass production process.
Once the interface passes the QC tests, the final firmware is uploaded.

And for an unknown reason, your interface missed the final firmware upload.

We apologize for that.
(it was no easy to identify the problem because it never happened before)