(this post applies to SharePoint 2010, 2013, 2016 classic sites)
So in this scenario, a user was unable to get new SharePoint 2010 sites to show in the top navigation, even though some where hidden. If this happens to you try the following:
- Navigate to Site Actions > Site Settings
- Under Look and Feel > Navigation
- In Global Navigation > update the maximum number of dynamic items
That’s it! now all your sites that haven’t been hidden will be displayed in the global navigation.