Eye gaze no longer registers

I'm brand new to Character Animator and I'm having difficulty diagnosing a problem. Eye gaze tracking has stopped working for my puppet. Blinks and eyebrows work, so I know the software is recording my face.

• "Eyeball Right" and "Eyeball Left" are assigned to no-stroke/no-fill ellipses behind each pupil.
• "Pupil Right" and "Pupil Left" are independent and assigned the appropriate pupil tags.

Is there something obvious I'm missing?

Thanks.