Sometimes when a device connects to the designer, instead of seeing the same view as that device, the screen is black:
This means that the A/B test designer is having trouble picking the activated view from your app because you have a view that is the default in your app but is not at the top of the stack.
In other words, Mixpanel’s designer is choosing a different view than what your app is showing. And since this default view is hidden from the designer, it simply displays a blank screen instead of what you are seeing.
The problem can be fixed by stacking the views in your app differently. You can figure out what view is making its way to the top of your app using the Xcode debugger.
If you would like further assistance with this issue or more details on how to resolve this issue, please reach out to firstname.lastname@example.org.