Volume envelope unable to make volume control points/handles

I have used the volume controls before in other versions on toonboom, but for some reason in my most recent software, I cannot click onto the blue line in the sound clip to adjust volume. I have checked “show volume envelope” in the sound menu, and I see the blue line in the center of the waveform, but nothing happens when I click on it – the little white boxes/sound adjustment handles don’t appear. I feel like I am missing some critical step in order to access the sound envelope control.

Try Alt+Click

Thanks so much! I couldn’t figure out a reason why I couldn’t just follow the tutorial and make it work. I guess it’s a Mac thing.