"How to Paint an Animation" ToonBoom tutorial Paint Bucket Tool not working

I have been helping my son and daughter learn the basics of Toon Boom. At the poiint where they need to learn use the Paint Bucket to fill in feathers on the bird (in the demo). The paint bucket does not fill. If we draw a box next to the bird and fill it - it fills in fine. We have followed the process of closing gaps and double checked quite a few times to make sure we are not missing anything. Paint Bucket does not fill in the feathters. What am I missing?

Perhaps the feathers are on a different layer (line art, colour art, underlay overlay) than
the layer that contains the feathers?

If you’re stuck, contact support to have a look at the project.