- carefully read and follow the brief instructions in the DM24 manual to activate HUI EMULATE mode on the mixer.
- connecting the mixer to the mac using firewire will not work easily on mac 10.15 - i am not sure if anyone has done it. for that u should use 10.13 or so.
- when u connect to the mac w USB, do you see the DM-24 in the MIDI network of your Audio MIDI Setup app? if so, it may only be Ableton that needs further configuration.
good luck!