iPad Unjailbreaking breaks App

[User1291]

So I was still running iOS 6.0.x.
Not only did apps start to require later ios versions, but also, apple threatened to release iOS8, which - as far as I heard - is rather iCloud-heavy (which is not a good thing).

Thus - and because iOS 7's control center could now at least partially replace the SBSettings - and despite my likely missing some features like the unrestrictor, I decided to unjailbreak my device before I was forced to upgrade to iOS8 if I wished to unjailbreak later.

Pretty much the standard way, too:
- backup
- reset (including forced update to iOS7.1.2)
- restore from backup

However, I now get a "The App GoodReader was not installed on the iPad due to an unknown error (0xe8000007)." in iTunes.
The app icon is there - grayed out, though - and clicking it will do perfectly nothing except change the App's name from "GoodReader" to "Waiting...".
I'd appreciate some help resolving this.

 

[dhlizard]

Use iTunes to remove the app from your device, reboot the device, then use iTunes to reinstall the app.

If it won't reinstall correctly, use iTunes to remove it, then reboot and try downloading it using iTunes on the device.