How can i fix the cd autochanger for my PHILIPS CCRT700?

I Brought my omega second hand, the radio and tape works fine, but the cd autochanger does not have any attemps remaining, and displays cd code (0) i have the key card with the code for the radio and the cd, but bcoz there are no attemps remainng, it will not allow me to enter the code. any advice other than changing the autochanger.