Change the alpha of the box (2nd argument of the ‘get overlay texture’ function on line 74) to see it in action. Basically, it seems that something changed between 3.1.1 and 3.3 about how Alpha is inherited down a control chain.
In a 3.1.1 project, you can have the alpha of the overlay box be 0 and add nonzero-alpha things on top of it and they’ll show up. This is useful so that you can pin things (in this case, target pips) to objects in the scene. It seems that the behavior of alpha changed. To make pips/healthbars/etc visible, I assume the fix would be “don’t use an invisible box as your container” but I’m not sure what would make a better container?