We've had that same thing! The inner clear casing dried up into a hard layer! I believe that it was because when the chick started to pip it was too weak to carry on, so it gave up and it was too late for the hen to continue pipping and the inner part dried, we then manually opened the egg being very, very careful to opening it, and it was successful, the chick made it out alive.Before you open any egg shells you should be positive that the chick is trying to pip, and has started to.
Also make sure that none of the eggs get rotated again once they have started to pip, this causes the chick to pip at the bottom, making no progress, and it will become too weak and will die.
Very sorry about the chick,
Best wishes,
-Birdbrain101