To be recognized by the lip-sync animation as a usable track, you will need to add your audio to the voice-over timeline.
You will notice that the ones in the music timeline are slightly green, while the ones in the voice-over timeline are blue.
Toonly: Why isn't my lip sync audio being recognized?
Learn why Toonly lip sync is not recognizing your audio and how to fix it by placing your audio in the voiceover timeline (blue) instead of the music timeline (green).