@thelewisimmers There are a couple of other things you can try fairly easily if you haven't done these already-- clearing your game cache and repairing your game through Origin.
To clear your game cache just delete the localthumbcache.package file from your Sims 4 folder. The game will auto-generate a new cache file the next time you launch it. You can try this first just to see if it fixes your issue. After you have deleted the file, restart your game and try testing in a fresh New Game rather than loading an old save. If you filter your CAS outfits by Custom Content the dress should appear in the "Outfits" category with its own custom thumbnail with the CC creator's name on it. If it works now you can exit without saving.
To repair your game through Origin:
While logged in on your Origin account
- Click on My Game Library
- Right click on the Sims 4 game tile
- Select Repair from the pop-up menu
This will do a scan on all of your Sims 4 system files (not your user files) and compare them to what is on the Origin server. If there are any missing or corrupt files then Origin will replace them. The scan will take a few minutes depending on your computer hardware. Wait for it to scan the base game and all of your packs. If you want to be extra cautious make back-up copies of your Saves, Tray, and Mods folders and keep them in a safe place like your desktop or an external drive before you do the repair. You shouldn't need them but I always do this just to be extra careful about things.
When the scan is done do a quick test on a fresh New Game.
If neither of these steps work then you might have to test to see if there is any other mod or CC in your Mods folder that is causing problems. It's a little more work but still fairly easy to do & we can go over that if clearing the cache and repairing through Origin do not fix things first.