"No importer found" for mp3 or m4a

I created a beat in GarageBand.

To share I "sent" it to iTunes (twice, once as an mp3, once as an m4a), when I went to Import in Alice I got the message:

Import Error
No importer found to load given file type.

I also, from GarageBand, shared by "exporting" to disk (it saved as m4a). When I went to Import in Alice I got the same message.

Any thoughts?