If you previously connected your game to a Facebook or Apple ID account, logging back in will restore your levels. To log in, tap the gear button on the upper right corner to access the Settings menu and then tap one of the log in options reconnect to your account.
 
If you have multiple accounts, please make sure that you log into the same Facebook or Apple ID account that was used previously.
 
If you need further assistance with restoring levels, please contact our Support team and we will be glad to help!