Keynote App has not downloaded properly and can't be deleted/reinstalled
I have attempted to install the Keynote App on my iPhone6. The app icon is currently dark with the announcement waiting... underneath - and its not working. I have tried reinstalling it, but the App Store considers me to have it already. I am also unable to delete it. I've also tried switching it off - all attempts to get it to do anything have been unsuccessful.
iPhone 6, iOS 8.3