There might have been some bugs preventing to unlock these, I'll make sure to give more insightful hints in the memories. I think you need to help the Rat King by giving him something to relax Cyril's entrance, then come back to check on the rat once you don't hear any business going on (you can rest a few times in the sewers, the rats should be too busy to assault you). Normally when you come back to click on the sewers exit, the rat will greet you again and take you to see Cyril.