Xcode 6.4 - Unable to set constraints on Views or ... anything

In my case, Xcode 11.2 somehow set layout property of my UIButton tranlates mask into constraints. So I changed it to automatic from size inspector and it is fixed.

This is because you remove root view from view controller. When you add UIViewController to storyboard you can see this:

If you delete this view and add UIImageView you see this:

So add UIView as root and UIImageView as single subview of root view. And then you can play with constraints:

if you move a View around (eg. move it IN then OUT a TableView) then it will mysteriously loose its ability to accept constraints. So build a new one. XCode 11.4.1