If you followed my directions, you should have two rpg maker vx ace windows running side by side. Project A and Project B.
In your game (Project A) click on your map and press CTRL+C. then in Project B click on the top object in the map window and press CTRL+V.
Everything on that map will be copied automatically.
The main issue was that your events on the ladder was set to action button. So the elevation would only activate when the player presses the action button while standing at the top of the ladder. I changed it to player touch.
I also took the default tile and made a graphic fix. I'm sure you'll like it.
Doesn't happen in the demo, so you must have areas on either side of the ladder that you can walk on. Perhaps change the passage settings to just up/down. Which is what the ladder is supposed to be by default.