I am using Mocha Pro AE 6.0.3 in AE CC 2019.
When I enable the Auto Fill option, nothing get filled in the AE composition. In the Mocha GUI, I think it works, but I have doubts I’m seeing it right. Looks like the canvas gets cropped to hide black bars but nothing gets filled.
After reading the doc, I’ve even tried duplicating my tracked mask + enabling the Fill from BG option to force Mocha to use a BG plate like the in Remove module.