title: oracle apex switch theme error "This application cannot be converted to a theme using list-based navigation"
body: <p>I am migrating apex code from 4.2 to 5.0. Before we used the theme "Light Blue - 15" and now in order to use the navigation menu feature, we want to switch theme to "Universal Theme - 42".</p>
  
  <p>When switching, one error window popped up and said "<strong>This application cannot be converted to a theme using list-based navigation, as it uses two levels of tabs. Please update the application and set current tabs settings to use only one level of tabs prior to switching the theme.</strong>" </p>
  
  <p><a href="http://i.stack.imgur.com/PjvAQ.jpg" rel="nofollow">enter image description here</a></p>
  
  <p>Then I checked my app current theme "Light Blue - 15" and it said this is one level tabs customized:
  <a href="http://i.stack.imgur.com/9jlM4.png" rel="nofollow">enter image description here</a></p>
  
  <p>Is there anything wrong? Can you give me some help on how to resolve this kind of error? </p>