OK, I will reply here first and then send a secure link with access.
I have reuploaded the image in Cornerstone and checked that it is in my media library - although it does say "unattached" but so do all the images that I upload only through Cornerstone...
This what I see in Cornerstone:
This is what I see on my incognito window:
As you can see, even the text under "FREE WELLNESS GUIDE" is different. It's as if none of the changes I make in Cornerstone are taking effect.