【Solution】Regarding to "Unable to get a valid license" when start the game

When you launched the game and had this pop-up window saying "Unable to get a valid license, please ensure that you have purchased this product."

Do not click "Retry" because it does nothing. Click "Buy" and redirect to Google Play (select Google Play when it gives you options), click "Update" to download about 3MB file, then you can play the game.

Here is the video to help you solve the problem.