We're aware of an issue with Facebook purchases for all King Games and our team is on it. π οΈ Hang tight while we fix things! You can still enjoy the game, and we'll keep you posted once it's solved.
You might get hands on some gold bars if you play the extra games in Farm Heroes but I think the best and fastest way is to purchase them in the game. Look out for the special offers that are shown in the weekends.