@hozzie14 How are you installing the custom content—sims3packs or .package files? If the latter, you need to use the same setup you'd use for mods. If you've installed sims3packs, try removing all the .dbc files from DCCache and then installing just one pack. Does it appear in-game? If so, you can go ahead an install a few more packs, test them, add a few more, test them too, etc. It's best to install only a few at a time, as the launcher doesn't handle large amounts of data very well.
If installing one sims3pack doesn't work, pull your entire TS3 game folder out of Documents and onto your desktop. When you launch the game, a clean folder will spawn with no content. Try installing one pack again in this clean folder; if it works, install a few at a time and keep testing. Once you've installed all the cc you want, you can move your saves and other content from your old game folder to your new one. Here's a list of all the files in that folder:
@hozzie14 Okay, that's store content, not cc. But the procedure is the same, except you're removing .ebc files from DCCache, not .dbc files. Additionally, be sure to delete ccmerged.package from DCBackup before you start. This file is necessary to make premium store content work, and if it's corrupt, you'll need to rebuild it.