2004 Honda Accord radio will not switch to the CD mode?

We just got our 2004 Honda Accord, and one thing that I noticed is that the radio will not change to the CD mode. The regular FM/AM radio works fine, and the display works too. There's a button labeled AUX/CD, and it is not responsive. All it does is change to the satellite radio. I've tried to long press all of the buttons, and nothing works. Does anyone know what the problem would be? Or any way to fix it?

Do you have a CD in the radio when you try the button? There must be a disk in for the radio to switch over.

If you do not have an owner's manual, you can download one for free on line.