unity – How do I find more details about a Vuforia error when going into play mode?

I want to make an AR app in Unity using Vuforia Engine. But when I try to enter play mode nothing appeared. Here’s the error alert:

Error alert in AR Camera properties

Since this error does not give me any clue about what went wrong, I’d like to know if there is a way to get more details about it so I can eventually figure out how to fix it.