Unable to sign in Sandbox gamecenter on iOS 7

Question

Since iOS 7 I no longer get the prompt from game center to ask me to log in sandbox mode when I open my application. I searched for a while and never saw any known issues ab

Answer 1

Seems there's been some change recently to work around this. Maybe in iOS7? This answer to a similar question https://stackoverflow.com/a/21231537/11801 suggests:
- quit your app
- use the settings page for gamecenter to log into your sandbox account, then log back out
- open your app and you should now be able to log in