Do you have a link to your AI file?
Sometimes when you divide shapes in AI it makes more shapes than necessary. One shape may be the one you are looking for then the other shape may be the divided area. In essence you aren’t seeing a hole in your work you are seeing 2 solids one being a positive shape the other being a negative shape.
If you have your file I could take a screengrab for you of what I mean. It is easier to find the pieces you don’t need from Illustrator rather than scrolling through the many masks in AE IMO.