You can enable MadMapper log by opening Tools menu with Cmd key pressed - Enable Log... => restart MM => menu Tools / Send current log. Then send a support request (mail to support[at]garagecube[dot]com specifying it's for Matthieu, I'll check the log then)
We'll see why MM fails opening the audio device for input. Maybe it just refuses opening with less than all channels available.
If you start MadRouter and press Cmd+D (or menu Tools / Show Devices), can you see you audio device ? It should show all available audio devices. Double clicking it should show its audio analysis channels (bass, medium, treble, amplitude, bpm ...), does it move ?