There are various reasons why a folio doesn't appear in your viewer application or the Adobe Content Viewer on a device. The following are a list of known reasons, and their resolutions.
The iPad version of the Adobe Content Viewer cannot display any folio that is not 1024 x 768. Adjust the dimensions of the folio in the Folio Builder panel by selecting the folio and choosing Properties from the panel menu.
Note: Ensure that your article pages share the aspect ratio of the folio so that you don't receive an error.
All articles in a folio must have the same layouts, horizontal only, vertical only, or both. The server prevents a folio in this state from being returned to a Viewer app.
If you use the add command, the orientation of your layout is dependent on the orientation set in the Document Setup. So, use of a taller document to make a smooth scrolling article can result in the wrong orientation. To avoid this issue, use the Article Import command with the *_h.indd or *_v.indd file naming convention instead of the Add Article button. Alternatively, you can add the document as with the intended orientation. Then, use the page tool to change its dimensions; the page tool doesn't change the document setup orientation.
It's a good idea to select the folio in the Folio Builder panel and choose Preview > Preview On Desktop at the bottom of the panel. If your folio contains articles with an orientation mismatch, an error message appears.
If you have imported an HTML article without using the *_h.html or *_v.html conventions, it's assumed that the article has both horizontal and vertical layouts. You can see the layouts in the Folio Producer Editor. Delete the article, rename the HTML to use the appropriate naming convention for the orientation of your folio, and reimport it.
If there are multiple folios with the same product ID, and they are not renditions (see Create folio renditions), the viewer displays the first folio. It ignores any subsequent folios with the same product ID.
By design, multiple folios that have the same Folio Name setting, but different dimensions, are considered renditions of one another. The server provides the rendition that most closely fits the dimensions of the device on which the Viewer is running. If you did not intend to use the renditions feature, ensure that all folios have unique names.
Only folios published as Free appear in the Adobe Content Viewer. Folios published as Retail do not appear in the Adobe Content Viewer. Any folio sourced from Acrobat.com (blue bannered) always appears in the Adobe Content Viewer, unless another issue prevents it from doing so.
Folios that are published with status Public and Retail must have a corresponding in-app purchase item defined in iTunes Connect or the Android developer site. Additionally, it's necessary that the folio product ID in the Folio Producer matches the product ID defined in the developer portals. Likewise, it's necessary that those in-app purchases are cleared for sale.
Folios do not appear in a custom viewer if the shared secret information is not specified in the Account Administration tool.
If you created a subscription app for iOS or a retail app for Android, copy the shared secret from the developer site such as iTunes Connect. Then, copy it to the application account in the Account Administration tool. The shared secret (iOS) is called the "public key" in the Google Play developer site and the "shared key" in the Amazon developer site. See Account Administration tool or the publishing guide for your platform: iOS Companion Guide (PDF) or Amazon/Android Publishing Guide.
Folios that are unpublished and contains two articles with the same name don't display in the Adobe Content Viewer of the device. To assess whether you're experiencing this issue, you can test the Desktop Adobe Content Viewer using the preview option in the Folio Builder panel in InDesign. You receive the following error: "'More than one article with the name "Name" is in the folio. Article names must be unique in a folio." Use the Folio Producer Editor to locate the duplicate article and either delete or rename.