Our iPad app associates files with a certain extension (.por) with itself. When it's installed, if users download one of those files in Safari, they're given the usual choice of which application to open it with. They choose our app (it's the only option listed) and the app opens with the new file displayed appropriately. Everything works just fine.
However, if they email that same file to themselves, and try to open the file from the standard iPad mail app, something different happens. The same list of "which app would you like to open it with?" appears with just our app in it, but choosing our app in the list does nothing at all, even if it's already running. The app does not open.
Opening files from email works fine for most users, and for me personally on our test iPads, just not for a few of these users. Restarting the iPad and updating the app doesn't seem to make a difference.
What could cause something like this to happen? Since our app doesn't open, I'm not sure how I could even debug this. Has anyone experienced this issue before?