1) Please first make sure that you have allowed the access in the Settings of your iPad:
Settings - Facebook - Magic Puzzles - on
2) If the issue still persists, try the following:
Open your Facebook page in a web browser -> Go into the Privacy Settings -> click Apps on the left -> Scroll through the list of apps that you've given Facebook permission to use -> Find Magic Puzzles and click X next to it.
Note: Just remove the permission, don't delete all the previous activity.
Then, please go back into Magic Puzzles and try to reconnect via Facebook. You should be asked to re-authorize Facebook to allow Magic Puzzles access.
3. If this doesn't work:
Go into your iPad Settings -> Scroll down until you find the Facebook app -> Tap the Facebook icon and re-enter your password for Facebook. You should see "Allow these apps to use your account" section below and the list of application -> Just slide to "on" next to Magic Puzzles icon to give it access to your Facebook. Switch off-on to reconfigure the connection. Then go back into Magic Puzzles and try to connect.