Take a look at this discussion/solution in the SanDisk Forum.
https://forums.sandisk.com/t5/SanDisk-Clip-Jam/audible-aa-files-how-to-activate-device/td-p/340919
Seems like you would need a one-time access to a Win-PC to activate your Clip Sport.
Then you could use iTunes on your Mac for all future access your Audible files (and copy to your activated Clip Sport).
https://audible.custhelp.com/app/answers/detail/a_id/4647/
ALSO, READ THE MESSAGE FROM SANDISK USER Lukasz7800 AT THIS LINK ABOUT MONO VS STEREO PROBLEMS
