Sometimes the App will start generating the download edition, rather than the 'read now' online version, before all pages have been created. Usually this will be pages carrying late evening results, breaking news or late news stories, for example the day after the Grand National.
The App will automatically create a blank page with Placeholder page over it. In order to see the page, you can relaunch the app and view the page again using the 'read now' online version, or try downloading the edition again. If you decide to download again, you must delete your original downloaded edition by visiting the 'Downloads' section within the app.