Very occasionally, there can be an issue in the download process of a particular file, and it doesn't fully download properly.
This could happen for a variety of reasons - patchy internet connection, some other part of the device's system crashed or restarted during download, or even just that it was taking a while and the device went to sleep while downloading. Zzz.
If this happens, you may find that particular files are not showing up in your showcase.
This might look like a red "warning triangle" showing up under the showcase thumbnail, or an error message that talks about an invalid pointer.
If this happens the first thing to try is to clear the cache, which can be done by logging out of the app and back in again.
To log out, you first go to the settings cog bottom left of the Home screen, and then from the Settings panel, tap "Log out" - which should be next to the email address of the logged-in user. When logging back in again, you have to re-download the showcases, but this will be an entirely fresh download (rather than just an update) and this should reset the cache.
To avoid this happening in general, try and make sure you have a solid internet connection when refreshing the app and/or downloading a file, and ensure you are using the most up to date version of Showcase.
If logging out and in again does not work as above, you can also try asking your Admin or Editor to re-upload the file in question, re-link it at that location, and re-publish the showcase.
And, if all else fails, remember you can always get in touch with the friendly team by emailing firstname.lastname@example.org. They're awesome and ready to help!