Login callback never fires under certain circumstances

[marwanhilmi]

Looking for advice on how to deal with the scenario where the login callback never fires. It appears that if a user exits the Game Center prompt, in some cases, the callback will never fire. Also due to restrictions in the native Game Center API, once cancelled, you can never fire a second Game Center request. We've also had other difficult to debug scenarios where the initial Game Center prompt never appears (nor does the callback fire).

Have you experienced any of the issues and are there any possible workarounds?