Or, they did listen and they don't have any questions because they are still processing that information dump and don't know what to ask yet.
You can't dump 10-20 years of experience on one person in 30 minutes and expect them to understand it all. Some might, but those are the outliers.
I'll mostly tell them to try it out and see what they can remember of the things I told them and we'll do the specific things they can't together. That way they get a fuller picture of the topic and you don't waste time by babysitting them with things they already know or remember.
But that requires that people trust you'll help them when they have problems.