There could be several reasons for cc not showing ingame. Please check each individual before contacting the discord’s debug channel:

• 1. Did you unzip the .zip file after downloading the content ? If not, check this tutorial here.
• 2. Did you put the CC files in your mod folder ?  Check this video if you don’t know how to install mods. 
• 3. Are the files not further than 2 subfolders deep ? Files shouldn’t be into more than 2 folders in the mods folder.
• 4. Did you enable mods in your game ? If you don’t know how, please follow this tutorial.
• 5. Is your game legit and updated ? If your game is a pirated version or is not updated to the last version, most of my cc won’t work.
• 6. Do you have the right DLC pack if the item requires one ? Some item are cloned from gamepack to be functional, check the description of the item you’ve downloaded to make sure you meet all the requirement.
• 7. Did you search in the right category ? Some items are not specifically tags were you would expect them. For example, the spiral stairs are under appliances, not in the buikd mode stairs.
• 8. It’s possible that your game updated to The Sims 4 Legacy Edition, and made a new folder destination for the entire game. It duplicates all the old mods to a new mods folder. The solution is to move all of the new CC from the old mods folder to the new one, located through The Sims 4 Legacy Edition.
• 9. Try to clear your cache files. Follow this tutorial.
• 10. Try to generate a complete new resource.cfg file. Follow this tutorial to know how.
• 11. There could be a conflict between several CC among your mods folder. You can try the 50/50 method to check if it’s the case. See more explanations here. 

Some items will need the cheatcode bb.moveobjects on to be able to be placed correctly.

It’s rare but some item are recolors and will need a mesh to be functional. Check the download page for further informations.

This will happen most likely if your game is not legit and/or not up to date. You need an updated game with the last version to be able to use cc correctly.

Some items can have buggy SSAO (ambiant occlusion). To fix this, you can completely remove SSAO from your game by follow this tutorial.

This bug most likely come from your nvidia card driver. You can follow this tutorial to download a fix for this. 

• 1. Always make sure that you download content directly from a creator page and not in included mods folder with build or repost blogs. CC sometimes need to be updated and fixed, so this is the best way to keep safe and working content.
• 2. Try to redownload the content by choosing the other alternative link. It is possible that sometimes the download process doesn’t go as planned and the files get corrupted. 
• 3. There could be a conflict between several CC among your mods folder. You can try the 50/50 method to check if it’s the case. See more explanations here.