On old device:

• Log in to Google Play / Apple or Facebook

• Make sure "Cloudsave" shows enabled and is green

• Play level to make fully sure progress is saved and synced with the cloud

On new device:

• Install the game

• Start the game

• Skip the tutorial (Settings → Skip)

• Login should be prompted → Log in with the same account you were using on your old account

• A cloud conflict should happen → Pick the first option “USE CLOUD DATA”