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

 

Brainium games use Apple's Game Center 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 Game Center in your device Settings using your Apple ID. Make sure you have a working, reliable internet connection to connect to and update Game Center leaderboards. For instructions and support on how to make sure you're logged-in to Game Center, please reference Apple's Game Center support page.