1) I think Edmund (and/or the 15-2138 documentation) can tell you how to get the 15-2138 to "blink back" or otherwise indicate the setup code number it is using.

2) Using a different device key (if you do it before finding that setup code number) program one of the three setup codes I gave you (make sure to first program the Audio device type with a 992 command if you pick a non-Audio device button). Then test several keys including the vol keys to see what works your receiver in that setup code.