Now that I see that response from the other forum, I see that you interpreted it correctly and used MakeHex correctly and generated the Pronto Hex that corresponds to the signals specified by that response.

I don't know why they don't work. Sorry, I don't know anything about the NEVO nor the Naim.

Do you have other functions of the Naim working with the NEVO? Or were On and Off the only functions you were going to use?

If you have Pronto Hex for any working function of the same device, that would help a lot toward understanding why the discrete codes you tried didn't work.