After doing some more experimentation, I also discovered that the Power On and Power Off 'buttons' on the Receiver page did not turn the Denon 2310 on or off, there was a Toggle Power "button" and that worked.

How can I determine if there are really discrete On and Off codes that will work.

What is strange is that the remote is definitely turning the receiver on and off, so I think it does have the right codes programmed into it, they just didn't seem to be imported correctly into the CCP software.