App does not receive NSUbiquityIdentityDidChangeNotification

Hello,

I'm trying to detect within my app when the user has logged in or out from iCloud. To do so, and following the iCloud Programming Guide, I made my app subscribe to the NSUbiquityIdentityDidChangeNotification. The issue is that the selector for the notification is never called.
Could you please help me ?
App does not receive NSUbiquityIdentityDidChangeNotification
 
 
Q