Did you allow Ableton access to your mic (which controls audio line-in) through the MacOS preferences? Open System Preferences > Security & Privacy > Privacy and select the Mic at the left, then tick the box beside Ableton on the right.

OOH!! That's why!

Just fallowed your steps. Now it works:)

Thank you very much, and happy new year

Enjoy!

i have the same issue but mic is enabled through privacy.

I also have no soundcard option at all for audio outputs in ableton and operating system.

pls help!

@Ryan > Did you perhaps miss the security setting while installing the drivers?

I'm having the same problem. I followed the instructions, clicking Allow when prompted in Security & Settings. DJM 900NXS2 is being recognized as a device, and when I view set it as an input on Sound settings in Mac OS, it appears to be getting a signal as the meter in the Sound settings reacts, but when I try Audacity or OBS there's no sound when using DJM 900NXS2 as the input device. 

I've also checked the mic enablement in Privacy Settings and everything is checked. I've tried uninstalling and reinstalling many times today and haven't had any luck. I've never had this much trouble installing anything.

Any suggestions beyond the link you already shared, because that isn't doing it.

Thanks