Go to Engrave mode, select page 24, right click and then click “Remove Page Number Change(s)”. Then select and right click page 24 again and click “Remove Master Page Change(s)”
Master Page Changes are overrides shown with a green line at the top.
Page Number Changes are overrides shown with a purple bottom-right corner.
ANY overrides mean that Dorico hangs onto the page, even if it’s empty.