Start with the basics!!

1.Put SB in realtime mode and confirm that the processor is firing commands. If the processor is sending commands then check your pinout.
2. Your pinout for that device is 2,3,5 like most others. A good practice is to check the pinout for each device that you are controlling at Crestron.com. Here's the link for your Denon AVR :

[Link: crestron.com]

3. If your commands are firing and your pinout is correct, you can then investigate defective com ports on the processor or AVR. If you have another device that you can control serially, hook it up and see if you can control it. If you can control it, then the issue is with the AVR. If you can't, the chances are that you have a bad com port on the processor.