This is a 2019 model Denon. I cannot get it to turn off and on with the Cox remote control. It's the 3rd receiver we've had. Both of the others worked fine with the Cox remote control.
Were the 3 receivers the same makes/models? What's the model number of your current remote? What codes have you tried already?
My bad...OP did provide the remote.
I found a few codes...
Denon
1360
1460
2134
2279
2516
2706
2820
2857
3347
3380
2134 is the correct number, but the receiver switches to tuner mode when powered on.
To be honest, I'm unsure which "receiver" is new: the cable-box or the Denon.
If the Denon is new, this would be an initial setup and we can work through this. If it's another cable-box, it's usually the authentication within the daisy-chain of HDMI cables causing an issue.
Which receiver is the new device?
