Ok, so thats a whole different situation, than what you described, or at least, I think most of us interpreted.
Are you saying you don't really know for sure if the other 13 channels ever worked? Or did you do a full test after you built it and confirm all 16 worked?
If the former, then its a build issue, meaning, you need to go back over the board and verify its built correctly, and as importantly, confirm you've got good clean solder connections.