Could it be that my IF/FW Mk ll is broken?
Or my firewire-cable?
Today I brought my iMac to my studio, connected the DM and firewire: same result as at my studio computer: the little volume monitor-control is greyed out on both macs:
See: https://imgur.com/a/PjzwC49
Since there is no way to adjust the volume. Because it's a proprietary driver, the icon is greyed out by default. Volume is - obviously - controlled in the mixer itself.