Copying Audio Files from One Audition Session to Another and Waveform Dissapears

I've opened up two different sessions in Audition. I'll copy a set of audio tracks from one session, and then paste those tracks into a different session. The files with their sound and waveform are there, but when i save it, the sound and waveform disappears. The original audio track will be perfectly fine in the main project folder, but I can't link the original audio track. I've tried deleting the media cache, but it still won't work. I'm working on a mac.