I have a set of redeem codes associated to a VPP purchase. I went ot my phone itunes and entered the first code. The app download started automatically. Unfortunately, due to a network problem, the download failed. Now returning to itunes I cannot find any way to re try downloading the app. Also re-entering the code obviously does not work (the code has already been used). So how can I re-try downloading the app on that phone without using a different code?
You can contact Apple's VPP support team and explain the issue. They should be able to trace the previous code and provide a new one.
The contact form is available here: https://www.apple.com/support/itunes/vpp/ (and they'll generally respond within 24 hours in my experience).
In the end I figured out what the issue is. The problem is that the App I was trying to redeem on iPhone was designed for iPad only. But this show a couple of issues on the App Store (IMHO bugs):
1) These is not check and no diagnostic at all. App Store just downloads the App and then gives a generic error message saying "there was an error.... try again later" that is totally misleading. It should check first compatibility and warns you before downloading the App and failing to install it
2) The code is gone anyway... there is no way to reuse the code even if the App cannot be installed.