From looking at the board the pic directly hooks to the LED. I would reflash that and check the 2nd pin down on the pic's left hand side from the screen printed side or the right from the back. Also check the orientation and solder joints on the 3023 particularly pin 1 if the in line led is not lighting.
Edit: and pin 2 of the 3023. if the in line LED is not responding. Now after rereading your original post if that is working and the channel still won't output, then I would move on to pins 4 and 6 on the 3023, the 180 ohm resistor and the triac (particularly the middle leg as they are notorious for being tough to get good heat on). If all of that fails, then I would probably say it was the triac and try to replace it.
