The Scores button is linked with Google Play Games, if the tab cannot be accessed, it is because you are not connected to Google Play Games.

 

Brainium games use Google Play Games to store scoring, and Achievement information and showcase leaderboard information. To ensure your scores are backed up and correctly updated on the leaderboards, login to the Google Play Games application with your Google ID. Make sure you have a working, reliable internet connection to connect to and update Google Play Games leaderboards. For instructions and support on how to make sure you're logged-in to Google Play Games, please reference Google Play Games support center.