IOS – How to i compare achievements with Game Center in iOS7

I am not aware of a way to force the updating other than running the apps to see if they will update things as a matter of course. Some app developers store the achievements in a way that they flow back from the game center - but it's more about how each developer chooses to use all the Game Center options.

Look for a much better experience when iCloud allows developers to store more app data in the cloud so you don't have to export/import and otherwise work to get your settings and loot to a new instance of the same app.

An alternate tack is to dive into the library of each app using a tool like PhoneView. You don't need to jailbreak the device - but often can find the folder where achievements are stored and you can put them back when they go missing.

I'm thinking that the server just must be down. I'm having the same issues logging into my game center on my iphone 4s. Perhaps it will fix itself within the hour as things like this apparently have happened before.