Gamer.SignedInGamers collection is empty

PC Windows 7.

I’m porting my XNA game.

In my games constructor, I create a GamerServicesComponent and add it to the Components collection.

After the games Update method has been called (as many times as you like), the Gamer.SignedInGamer collection is still empty.

Is there something else I have to do to get a SignedInGamer object? (which I need to create a NetworkSession).