Pat, have you tried clicking / tapping the Reset button? Do that, then turn the sound on and refresh the scoreboard while on the same puzzle. (If you change the sound setting as the last action you take at a particular puzzle, your change won't be saved.)
If that doesn't solve your problem let me know. I can fix it by changing the database directly, but that shouldn't be necessary.
I probably should change the way sound preferences are recorded anyway. It doesn't make sense to have the same setting for a player on every device - you might want sound on your PC and silence on your tablet, or vice versa.