Why are certain slides hidden when not hidden in Properties?

Good morning Blesy. Welcome to E-Learning Heroes!

I apologize for the delay in response. I noticed you opened a support case (00306520) over the weekend. I see that John was working with you on the case and he gave some information about the hidden slides. Did this resolve the problem for you?

Hi Christine,

Let me try John 's suggestion and I will get back to you on the same.

Hi Blesy,

Thanks for getting back to me! The latest activity on the case was from John on 11/26/2012 at 9:02 AM. You might want to check and make sure that the email didn't go into a spam folder. I'll provide the information he sent you in this thread, but if you're able to locate the message he sent, you can respond with any updates to that message and it will update your case automatically. 

Here's the information:

Child slides will inherit the "hidden" value of their parent slide in Slide properties. So slides on level 2 will be set to hidden if their parent slide (level 1 slide that immediately precedes the level 2 slides) is set to hidden. 
To avoid issues with setting levels and using hidden slides, I would recommend doing the following general steps: 

1) If you have any slides hidden, un-hide them first. 
2) Set the proper levels to all your slides taking note that child slides will inherit the parent's hidden setting. 
3) Set the slides to be hidden in navigation only after all slides have the proper levels.