I wanna sign in with Google+ to claim 100 gems. But when the server tried to link my account, it always said "Link failed". What could be the problem and what should I do?
I had this problem, but it straightened itself out the next day or two. Make sure you try to authorize the account everyday. If you don't have that Gmail account selected on your device, follow this:
Go to Settings - Choose the option “Change Account” - Choose the Gmail account you use in-game.