Have you grouped the icon image and the button together?
I know it might seem obvious but I've been confused sometimes when clicking only on the picture placed on top of the button, and not on the button.
Thus having an empty "Hide when" as you don't really need to hide the picture.
Am I making sense?
I wasn't aware of having an actual button, I just inserted a picture and right-click and 'button setup'. Using the picture as the button. I even mixed up the two terms in my original question.
This seems to create a group of objects, the button and the picture and they're grouped together. When ungrouping them I can see the calculation once again.
No problem, happy to help! I know how much buttons can be confusing sometimes, especially when you create them from a picture
Just for this situation, if I must have a graphic (that is not an icon in a button), the I like to overlay an object (fill none) and make that the button. It means checking layers to get to the graphic, if needing changing, but it does solve this problem.