Custom content is not showing up in the game

If your downloaded and installed custom content for The Sims 4 does not show up in game (or not showing up as expected), there can be various reasons for that:

No CC shows up in game

• After most official patches, the game will automatically disable the use of custom content in the game settings. To make it show up again, you'll need to enable it again manually in the game settings, and restart the game after that.
• Make sure your content is placed in the right location on your computer - see Installing content in The Sims 4.

Some CC does not show up in game

• Some custom content will need a certain Expansion, Game or Stuff Pack for it to show up in game. The description of the downloaded creation on TSR should in that case give info about what is needed.
• Some creations can be made as a recolor variation of an in game item, instead of showing up a seperate item. Those can sometimes be hard to find. When using the game filters for only showing 'custom content', creations should be easier to find.
• Some CAS creations will only show up if you remove the default male/female setting in the filter.
• Some creations will need the game to be fully updated to show up correctly. This can be the case when something is cloned that was added by one of the game patches. Having an unpatched game or a non-official version of the game will cause some CC to not show up in game.
• Lots, rooms and Sims that are not showing up in your Gallery might also need a specific Pack or other custom content that is currently not installed on your computer. By default your Gallery will hide Lots and Sims that need something that is not installed. In the Gallery settings you can change the settings to make those Lots and Sims show up as well.

Part of the CC is not showing up as expected

• Some custom content needs a mesh (the actual shape of something like a hairstyle, clothing or object) for it show up correctly in game. In this case you can see the thumbnail for the creation, but it's not showing up as you would expect. For instance for missing hairstyle meshes you'll see a bald head instead of the hair you've seen on the previews.  For clothing you'll see missing body parts. In some cases you'll also see a weird blocked texture on the Sim, with question marks on it.  To make the creation show up correctly, you'll need the mesh that was used to make that creation. The description of the downloaded creation on TSR should give information about which mesh is needed, and where to download it.
• Lots, rooms and Sims often need extra CC for them to show up as shown on TSR. Read the decription of the Lot or Sim on TSR about info on what is needed and where to download it.  These content types also need to be installed a little differently in Sims 4.  This is explained here.
• Some (mainly older) CC skintones can cause other (correctly made) CC to not show up correctly. This is for instance the case with mermaid tales. Use a different or updated CC skintone in that case.

If non of this helps, check that your custom content was installed correctly:  Installing content in The Sims 4