For the past few days I have not been able to open Game Center on my iPhone 5S running the latest version of iOS 9. When I press the app, all that opens is a blank white screen. When I go into settings and press Game Center, the settings for Game Center do not open- it just freezes on the Settings menu. When I play a game connected to Game Center, the game says it cannot sign me in to Game Center. I am running the same version of iOS on an iPad mini 2 (which also has an A7 processor) and Game Center works just fine. Does anyone have any ideas?