Hi Mark!
So there is a notation that gets added to profiles where during the creation process nothing is added into the last box on the page marked Sources. A profile can be created without sources, but it's generally not preferred. However, living persons or persons who might be challenging to find sources for can be created this way.
So this notation (looks like "{{Unsourced}}" ) is generally found at the top of the biography section. Even if you add sources, it won't automatically go away. You still have to delete it. Once you delete this, the large warning box will go away.
Hope that helps.