After you tap an album to include it in the game, please don't forget to deselect the albums that you don't want to be included.
It may require scrolling to the bottom of the library and checking all of the subsections.
Then return to the home screen to play the album.
If that doesn't work, please try reinstalling the Words app, restarting the iPad, and updating your iOS.
If the above doesn't help, please write us at email@example.com with a screenshot and the myOsmo URL of the Words album that isn't working for you!