Are you using any cheats or a mod of CT? Something may have broken the game.
If you're playing on a console, have you tried pressing A? Some parts of the game (like Lucca's red gate adventure) have kind of obscure directions. Also, try moving the shell either more or less.
If these don't help, try to take a screenshot or video or even snap a photo of your screen with a camera and post it here and somebody can probably help better.
If all else fails, there are many walkthroughs on youtube that should be able to show you what it's supposed to look like at least.