I just finished the main game on XBOX 360 and I'd like to play Treasures of the Sun but I can't find a way in. According to multiple online sources, you can access the DLC by loading the last autosave: "from inside the Causeway after defeating Jeyne at the top of the Spire, but before entering the Rukkenvahl Chapterhouse to get to the final battle. There will be a new section of the causeway, with a note hanging on a section of rock in the center. Simply read the note to start the story." I loaded the last autosave and I'm exactly in the Causeway as described in the guide but I can't find the new section of the causeway (actually a new section of the causeway is shown on the map but it doesn't appear in the main window).
The Downloadable Contents menu options shows Treasures of the Sun as Available.