If you've just re-installed, Do you have your old device with you? Do the following:
  • When the game launches to the initial Splash screen, please tap on the Cog Button under the Play button:
     
    • Tap Link Device
    • Choose This is the Old Device
      • Grab the randomly generated Code
        Launch the game on your new device
    • Choose This is a New Device
    • Enter the Link Code you were provided
I don't have my old device. I remember the username I made though!
  • Contact Customer Care in the game by tapping:
    • Settings
    • Help/FAQ
    • Tap on the top right where it says Contact Us
    • Let us know that you’re looking to recover your account and present us with your username and information about your account (Venue/Chapters/Keys/Gems/Coins)! If you had screenshots of your game, that’s an added bonus!

You can also recover your account via your attached Email or Social Login.