Why does Platform Trim not work on Platforms? [ Edited ]

[TylarTyger]

I've been looking around everywhere on how to fix this bug. I just started to use platforms in build mode, when I tried to change its color using the platform trims, it wouldn't change. I would get a red error box if I touched the side to change it saying, "No changes to be made". If I try to do the same thing but from the top view, I get another red error box saying, "Must be applied to a room". I tried using half wall trims as well, as wallpaper and flooring. Only the flooring will apply to the platforms. I don't have any cc downloaded, and the Sims 4 packs I have downloaded are; Cats & Dogs, Paranormal, Tiny Living, Laundry Day, Toddler, Fitness, Vintage Glamour, Romantic Garden, and Perfect Patio. We've downloaded most of this since January of this year. I have not previously tried using platforms in build mode, and was unaware of this issue until recently. Another bug with platforms is that I cannot attach stars to it to allow my sims to get in and out of the house. Is there any fix to this issue with Platforms?

[JonaO703]

@TylarTyger Hello!  It might be helpful if you could take some screenshots of your build so we have a better idea of what's happening. 

In the meantime, when you select the platform trim you want, hover over the floor of the platform and click there to add it; just as if you were placing carpet or tile.  As for the stairs, I've found they can be really tricky.  Make sure you have a full brick of space at the top and bottom of the stairs for sims to enter / exit.  Also, the stairs landing can't be off the lot.  Hope that helps but if it doesn't, let us know. 

[TylarTyger]

@JonaO703 The stairs was very, very helpful! I'll try to upload some screenshots of what's happening