Disc changer not reading!

I replaced the car battery and now the Blaupunkt IDC - A09 multichanger in my 2002 Fiat Punto Sporting has stopped working. The radio and tape player worked straight away but the cd unit is not reading cd's or not ejecting them. I have the code for it but the stereo hasn't asked for it and the lights 1-5 on the changer are flashing between Green and Yellow. The battery had been disconnected for a few hours whilst I went and bought a new one.

Any ideas??

Thanks