Alfa 147 +MP3 player

[PJS917]

I have a 6 month old Alfa 147 with standard fit CD/radio. I have bought a Blaupunkt auxiliary in harness that allows it to play MP3’s. When pressing the SRC button the radio should go FM/FM2/FM3/MW/LW/CD/CD-D. CD-D being the line input. However, the unit is not recognising the new connection. Has anyone fitted one of these or does anyone know how to get the unit to work?

Thanks