Unresponsive UIButton in subview added to UIStackView
I have had the exact same issue: a StackView which contains views. Each view contains a button and a label. The views are only containers for layout reasons.
In my case: I did not give the view a height constraint and it seems that it had a zero height (after changing the background color for debugging I did not see the view), but the button and label was visible (but unresponsive).
After I have added a height constraint to the layout view the (debug) background color was visible and the buttons responded as expected.
In my case, it was the aligment property of the StackView that was causing the problem.
When I set that property to Fill instead of Center the problem dissappeared.
I just ran into this issue myself. In my case, I had a UIStackView as a subview of my UIButton. I needed to set isUserInteractionEnabled = false on the stack view in order to get my button to work. This is probably a wise thing to set on any UIButton subview.