Hello! Are you using an Android tablet? There used to be a bug where the codes weren't showing on tablets, but it was fixed soon after. If you're using a tablet, try downloading the latest version of Shelter/Demons Within and it should work. The code appears when you click the node of the story that is completed and, if it's not clear, to get the code to unlock the first chapter in Demons Within, you need to finish the Prologue in the Shelter game and get the code over there.