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.
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
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:
