Sorry to hear you were having trouble. I was so looking forward to seeing you jamming with the output expander. Don’t worry, though. I’ve been able to get every single build I have attempted running fairly easily.
The DAC is the trickiest part of the Build. Check the connections between the teensy and the backboard first before going through any major surgery. A cold solder joint on the pins that matter can leave the DAC dormant. The schematic up at the site has all of the pertinent details. If you need more help, please PM me.
Do your LEDs light up? They are controlled independently and should still function even if the DAC is not connected properly.
The pesky balance pins have gotten me twice. You will have to remove the Jack for TR 1 and reduce the size of the pin that pokes through underneath it. In my building tips, I recommend trimming that to be board level before installing the jack. That said, I’ve been able to successfully trim it down after first assembly on a number of occasions. Just the desolder the two pin header, take it out, trim the pins, and then re-solder it flush.