Media Button not working

I have just bought a 2006, Mazda 5 NAV 2.0l Diesel with in car entertainment system. According to the manual, to get the DVD audio coming through the system, I need to simply press the Media button on the radio. This does not do anything. Does not beep, just does nothing. Any thoughts as to what the issue might be?

Thanks

The 2006 radios without navigation require pins 1 & 13 to be connected in the back for the "media" button to do anything, at which point it passes audio through from pins 3 & 4 (left channel) and 5 & 6 (right channel) to the amplifier. It may be possible that this connector is loose or disconnected, or that the internal connection to enable the "media" button is broken.

This thread has more information on the modifications to the base radio, so you know what to look for
http://www.mazdas247.com/forum/showthread.php?123778670-How-To-Make-an-AUX-input-for-FREE