Check the following:
- If you built an app with Enable Preview selected, click the Preview icon in the Content & Layouts section of the Portal to make content available in the preview app.
- Make sure that you have created a collection with at least one article and that you added that collection to the top-level collection. The top-level collection is called either "default" or "default phone" and "default tablet," depending on your project settings.
- Make sure that your content is available in the app. For example, if you create and publish a collection, remember to add it to an existing collection so that users can navigate to it.