@Ninaxalaia Sometimes a file in DCCache gets corrupted and prevents custom content from installing properly. There can also be issues with other files related to custom worlds, so rather than sort through all of that, it may be easier to start with a clean Sims 3 folder, then move your existing content to that folder.
Move the entire Sims 3 folder out of Documents\Electronic Arts and onto your desktop, open the launcher to create a new folder, download a fresh copy of one world, install it, and see whether it shows up in-game. If it does, restart your computer and check again, just to be thorough. If everything is fine, you can install your other worlds as well as your non-world custom content; you can probably still find the Sims3Packs in Downloads inside your old Sims 3 folder. Please install only one world at a time, as in, not in a batch with anything else: the launcher doesn't handle large amounts of data very well. Smaller cc files can be installed in groups, but even here, it's best to limit the number of items in a batch to about six, or fewer if you're installing a large set.
Once you've installed all your custom content into the new folder and confirmed it's showing up, you can move your saves and other content from the old folder to the new one. Here's a description of everything in that folder:
https://sims3.crinrict.com/en/2011/01/faq-user-files.html
If you have questions about what to move or how to do it, just let me know what step you're having trouble with.
