I am also having this exact same problem. Brand new Quantum 2 Interface. Macbook Pro. Logic Pro X. After installing the unit, I had sound everywhere but was immediately prompted to update firmware. Now I have no sound coming from the unit on outputs 1 & 2 and 3 & 4 , nor do I have sound coming from the headphone jack. Only when I select "input monitoring" in my DAW, can I hear the unit. It records fine but I need to hear whats going on during recording. Frustrating.