See the screen shots below of the Employee example from the enaml distribution.
The checkbox does not show it's selected value when the window loses focus. I've seen this behavior in my code and now I see the example also has this problem.
That behavior is outside of Enaml's control. It looks like something Qt is doing on its own to try to blend end with the platform look-and-feel.
To be clear, the checkbox does show its state, the check mark is just a very light gray.