July 2020
@Caiyah14It looks like the file path for your user folder is set up for the Legacy Edition of Sims 4 rather than the standard version. When you launch the game you'll see the version number way down at the bottom of the main menu page. It will look something like this:
Don't worry about the first 3 sets of numbers, this is an old screen-shot and they have changed since then, it's only the last four numbers we need to look at here. The last 4 numbers should be either 1020 or 1520 and this will tell you which version you are using.
1020 = PC standard version
1520 = PC Legacy Edition
When you look at the file path for the Mods folder you are trying to put new CC into is it:
Documents > Electronic Arts > The Sims 4 > Mods
Or is it?
Documents > Electronic Arts > The Sims 4 Legacy Edition > Mods
It seems like I remember reading about an issue like this a little while back-- I'll do a little more research and update this thread if I can find it. I might just be remembering wrong though.