I have been using the AR12 USB 24bit/96kHz flawlessly for a couple of months now with Logic Pro X on an iMac. Suddenly, having changed nothing intentionally, I can no longer hear anything coming out of the mixer. It records tracks which can be played through my iMac speakers. But I can no longer listen to any previously recorded audio through the mixer itself. I have tried plugging my headphones in directly to the headphone jack. I am running OS 10.12.3 (16D32) with a 2.7 GHz Intel Core i5.
Update: I have the same issue with Garage Band. Can record through the AR12, but there is no playback through the AR!2. The audio output is set the studiolive AR12 on both logic and garage band.
I had the USB/SD card return set to SD CARD instead of USB.