Not All CC Shows Up

You're not installing the files to the right place, it seems.

If the download is in package format, meaning it is clothing, hair, makeup, objects, etc. Do not try to open the package files, simply place the package files into your Documents\Electronic Arts\The Sims 4\Mods folder. The game can not be running when you do this. (If it's a set, it might be in a zip file and you will need to right click to open the zip file first.)

If the download is a house or a sim, unzip the file (right click and choose Open on the zip file) and place all of those files (between 5 and 9 files) into your Documents\Electronic Arts\The Sims 4\Tray folder. The game can be running when you do this.