This was discussed last month (on the Mac subforum) and it looks as if the issue was fixed?
But I am seeing the same bug on Windows…
When I first select an object with multiple fills the Delete icon is greyed out and unclickable.
Clicking on the current fill (which should be unneccessary) does not enable the Delete icon.
Selecting a different fill does activate the Delete icon.
Right clicking and choosing Delete does work.