Make sure your game is fully updated.

How to set up a room with platforms in the game:

- for a room to work correctly, after setting it up in the game, you will have to add a ceiling or another room on the top as a second floor.
- how to add a ceiling: Open build mode, go into the Walls and Empty rooms section and pick the - Flat Square - option, place it on the top of the room as a ceiling, this will ensure the room will work correctly. If you don't add a ceiling, a second room upstairs, or a roof, this can make Sims more vulnerable to cold or heat.

To install this room into your game:
- download the room
- unzip room files
- copy room files and paste them into your Tray catalog ([...]My Documents/Electronic Arts/The Sims 4/Tray]
- all CC - objects from --> Required Tab go to the Mods folder.

I have installed packs:

Expansion Pack
Get To Work
Get Together
City Living
Cats and Dogs
Seasons
Get Famous
Island Living
Eco Lifestyle
Discover University
Cottage Living
Snowy Escape
High School Years

Game Pack
Outdoor Retreat
Spa Day
Dine Out
Vampires
Parenthood
Jungle Adventure
Strangerville
Dream Home Decorator
My Wedding Stories
Werewolves

Stuff Pack
Luxury Party
Perfect Patio
Cool Kitchen
Romantic Garden
Kids Room
Moschino
Tiny Living
Spooky
Laundry Day

Industrial Loft Kit
Blooming Rooms Kit
Desert Luxe Kit

Free:
Holiday Celebration Stuff
Grim's Ghoulish Guitar


Cheats I've used:
debug
bb.moveobjects

Credits: All TSR CC's Creators