If you want to login to your old account and already bound your account with Google+, Facebook or Email, you can try to follow this instruction. Please tap the More button on the main screen of your game. You will see the screen as below and continue by tap Account Info.
After you tap the button, you will see the screen as below, from here please tap the Switch Account button.
You will see the screen as below, please choose between Google+, Facebook or Email button.
If you want to Switch your account to Facebook, please remember to login your Facebook Account that you already bound to your game account in the Facebook Apps in your device. After you confirm that it's done, you just need to tap the Facebook button in this screen and wait until the successful message show in your screen and restart the game.
If you tap the Google+ button, you will see the screen as below and for information this will follow the Google Account that you have already enter in your Play Store, so please remember to login with the Google account that you already bound with your account. If you already confirm, then continue by tapping the Google button and wait till there's a successful message show in your screen and restart the game.
If you want to Switch with Email, you will need to enter the correct Email and password that you have bound with your account.
After you enter it correctly, you will see a successful message show in your screen as below and restart the game.
If the above answer can't help you solve the issue or didn't answer the question, you can reach our in-game customer service by clicking on "I NEED MORE HELP".