The game only restore progress when a clean install is done (that means the game is not on the device and the game is installed from the google play store with zero progress) and the user is signed in already with the account he played on before.
Now with example:
Let's say you played on google account example1@gmail.com
Then first double check the user is signed in on the google play store with example1@gmail.com
Now install the game from the google play store.
Again: please note the user is already signed in on that google account, before he installs the game.
On boot up from the game, the game will detect example1@gmail.com and it will ask the player if he wants to continue the game with the account.
And if all of that still does not help. Please check our video again, which explains more about the Google Play Games app:
https://play.google.com/store/apps/details?id=com.google.android.play.games&hl=en_GB
This Google Play Games app is where your game progress is stored. If your game progress was not restored, then is because you are not signed in under the correct google play account in this app first. Make sure you are signed in under the account in which you played the Dynamons game.
Please check out to this movie for more information:
https://www.youtube.com/watch?v=vH-iiRSJ1Qc&t=179s