Make sure your game is fully updated.

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
Snowy Escape

Game Pack
Outdoor Retreat
Spa Day
Dine Out
Vampires
Parenthood
Jungle Adventure

Stuff Pack
Luxury Party
Perfect Patio
Cool Kitchen
Romantic Garden
Kids Room
Backyard
Vintage Glamour
Toddlers
Moschino
Tiny Living

Free:
Holiday Celebration Stuff
Grim's Ghoulish Guitar


Cheats I've used:
bb.moveobjects
debug

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

CC's needed for this Room - Please read in the Required Tab.

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.

Credits: All TSR Artists!