Hi I am trying to add game center to my iphone app. I have done the following steps
1) I have added an app to my itnuesAccount
2) I assigned the Bundle ID as net
Many reasons are there for this problem
Add your app on itunesconnect.apple.com
Fill all information (Make Sure your available/publish date)
Can enter dummy data, but bundle id and name must be original as your real game.(Can't change)
then put your leaderboard/Achivement id in your app.
If still you getting same message "Game Center is not recognized this game", check your availability date which you have enter while filling the information of your app on itunesconnect.apple.com. This date should not be after your current date.
If again you are getting same problem then upload this app on AppStore. (After checking you can reject this uploaded binary)