I would also say it will probably just take time. We are using Bigger
... this year with my dd 8 and my ds 10. We have always done read alouds, and they've both learned to sit and enjoy even long periods of reading. However, we'd never really done narration. DD has some experience with the questions since she went through Beyond
...but ds does not and neither one knows how to narrate, really. We are working on improving their skills.
I think if you ask them the question and you think they really were listening, then it's okay if they can't answer. The pp's advice was good...you could go back and read the specific passage and try again. Or, you could just say "that's okay, this is what I was looking for...." and then tell them the answer. They are young, it's something new, and it takes us a ll a while to learn something new sometimes. They'll get there as they mature. HTH