Sorry, to clarify:
Featured image is now appearing as expected on PAGES.
On POSTS, it appears that the featured image was added to the top. What I mean by this is that the top image appears as expected, but the feature image is duplicated, appearing above the post title. Rather than replacing the full size display of the feature image with the slider/header size, it now has both.
I have tried to fix this by editing the post: going to the bottom of the page where it says HELENA OPTIONS > SINGLE PAGE POST IMAGE. Here I select DISABLE, hoping to remove the additional image, but nothing happens. If I select another option, like making this duplicate image a smaller size such as HELENA SMALL or POST THUMBNAIL, this duplicate image does change to the smaller size. But I cannot get rid of it.
I hope this helps to clarify the issue.