Ceiling geometry is not generated as expected.
Warning: Ceiling sketch is invalid.
Issue: Revit failed to regenerate the ceiling geometry upon executing your last action.
Solution: You cannot ignore this warning. You must cancel the action. This error might occur if you have sketched an opening in a ceiling, and then locked that opening to another element, such as a wall. If you move the wall, the opening moves with it. If the opening should suddenly lose its host (the ceiling), this error would display. You can edit the ceiling sketch and then attempt the action again.