GameKit authenticateWithCompletionHandler stuck

I'm having a classic everything-worked-yesterday-nothing-works-today kinda day.

I set up Game Center yesterday. Managed to log in, get leaderboards, get achievements etc.

Today, everything stopped working. authenticateWithCompletionHandler doesn't call the completion handler, even for an error.

I tried several iPhones, rebooting开发者_Python百科 them, rebooting the mac, deleting and installing the app and more (all hints gathered from the internet).

I figured it was a temporary Game Center Sandbox issue, but then noticed it was working fine on the simulator. So I retargeted my own code, had another reboot, and now it doesn't even work on the simulator!

When I try to open the Game Center App it's in "Loading..." state, and doesn't get out of it.

What am I doing wrong? What happened between everything was working, to nothing is?

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Log out of your current GameCenter account in your iphone.. Install the app again and launch the app.. Note that it should prompt you to sign in.. If not, check your codes to ensure that it calls the function to authenticate the user is being called..