3 solutions come to my mind:
1) try to use CD0 from AmiKit:Storage/DOSDrivers instead. Move it to AmiKit:Devs/DOSDrivers and restart AmiKit.
2) Before you start AmiKit, insert CD to your Mac, star AmiKit Launcher and select Configure. Then in CD&HardDrives section select Add Directory button and enter:
Device name: CD3
Volume label: NameOfCD
Path: select root path of the CD
3) try to use other source than AmigaOS4.1 FE CD (which contains AmigaOS3.1 which probably doesn't support CDs... I am not sure as I am used to AmigaOS3.9)
Hope it helps.