Audio Disappears?

My situation: I’ve loaded up Harmony and put in the sound file I want. It works perfectly, and I animate following the sound file. I save my work, and put it away. The next time I open the file, all my animation is there, but Toon Boom “can’t find the sound file”. I have to go back and refit all the sound to the animation.

Am I doing something wrong? How do I fix it?