I can't mute when I slide down the thing that's on the side of the iPad. I used to be able to do it only last week and for some reason it doesn't work anymore its not the settings because I selected it to mute when I do it. It's really weird because when I select the screen lock and slide the side thing down it screen locks so it seems like that it just doesn't mute when it suppose to. I don't know what to do. I got my iPad 2 refurbished... Should I take it to apple store?