When you say "To simplify lighting code development, made a lighting simulator using a 30-channel DMX control board with RGB LED modules connected to each of the channels." does this mean you made the test rig?
You have not posted your sketch and schematic so that makes diagnosis more difficult but from the way you describe, it sounds like the DMX reset and/or start mark timings are not suitable so the entire universe is ignored. If you made the test rig then maybe you can loosen the timings or hack DMXSimple to get better timings.
Another option might be worth testing with a different DMX library to see if that cures the problem as you will then know if the fault lies with DMXSimple or something else.
If your using that library to free up the Serial port then maybe consider using a different arduino like the Leonardo that has a native USB serial port and a UART port. I made a simple DMX tester using this method here.