P38 Harman Cardman x6 Multichanger CD?

Hi,
I have a P38 Range Rover, and have got a problem with my CD changer.
I can load all the six CD into the magazine then insert it into the auto changer, it goes through all the motions of selecting all six CDS. I press the cd button the radio and nothing happens it just says NO DISC on the radio display screen, what can be the problem!! and can I fix it?