Cats + Dogs Expansion Pack Won’t Load in Game No Matter What I Do!

@evicopperfield  I've just read your messages, and first of all, the reason the CAS Demo folder keeps being renamed may be that your antivirus is blocking the change.  In that case, disable it, change the name, then reenable the antivirus, or leave it disabled until you've tried downloading the packs again.  It's also possible the EA App is blocking the rename, in which case restart your computer and make sure the App isn't running in the Task Manager.  Look for the EABackgroundService under background processes as well, and shut it down if you find it.

Otherwise, some players have reported that moving the folders works, although it doesn't for everyone.  In your case, you'd go into this folder:

C:\Program Files (x86)\Origin Games\The Sims 4 Create a Sim Demo

and drag the EP04 folder into this folder:

C:\Program Files (x86)\Origin Games\The Sims 4

Then you'd clear the EA App's cache (again) and repair the game, and see whether C&D loaded.  If you do use a third-party antivirus, you might need to disable it while moving the folder as well.

there’s 2 of each. one is CAS installer & the other is just CAS demo. then the sims 4 game one has “ts4/delta” & then “ts4/delta/EP04”. which ones of those would i move?

@evicopperfield  Ignore anything with Delta in the file path.  Delete any EP04 folder that's within an _Installer folder.  Move the EP04 folder that's directly within the CAS Demo folder to directly inside the proper "The Sims 4" folder.

Okay it still hasn’t worked. Do you know how I would disable the antivirus?

@evicopperfield  That depends on which antivirus you're using.  Most have documentation online though, so just run a search and find a guide published by the same company.

The other reason you might not be able to rename the CAS Demo folder is that the EA App is open or the EABackgroundService is still running.  You can close both in the Task Manager.  This shouldn't revert a change to a folder name, in fact it just throws an error when you try to rename a related folder; I'm just mentioning it in case you see that error.

If you have no use for the CAS Demo, the path of least resistance here is to simply uninstall it.  That's easier than jumping through all these hoops.

If you do want to keep the CAS Demo, and you manage to rename it, be sure to delete the EP04 folder from inside it before trying to download Cats & Dogs again.