Yeah I'm not sure what's going on there, at the very least the new content in the sixth dungeon should be easy to find, and a brief test on my end shows it's working.
From your comment, it sounds like you downloaded the base version 0.54 and then patched that, but I just want to confirm that is what you did. If you just applied patch 0.54.2 to your 0.53 version of the game, that could be the issue, as that generally causes problems.
If that's not the case, a brief overview of what's been added and where it is so you can double check. For the sixth dungeon specifically, the new content is where the old dead end was. Up from the tiny room you first enter on the purple floor, go left of the purple goo hallway then up. Additionally, if you are far enough into the sixth dungeon (about halfway into the second floor specifically,) there should be a new Alexander scene that triggers when you enter the sixth dungeon each day. There is also a new date scene with Katie, though it's for a submissive Katie, so if you are on the dom route you wouldn't see that, and there's a new Beatrice scene that requires you to have seen her second dick growth scene as well as reach the halfway point on the second floor in the sixth dungeon.
Lastly, there were 3 CG sets added, so another thing to test would be to go to the scene reviewer. Assuming you've completed the third dungeon, there should be "Cursed Book 3/Curvy Slime" near the bottom, which is from the new update.
Let me know if you're seeing any of those things, and if not let me know so I can try and figure out what's going on. Thanks.