I've been trying to reduce my downloads folder so that it’s not so laggy when I play so I first tried to remove any duplicate files. However somewhere along the way, I must’ve deleted the wrong thing and therefore my game would not load. So I removed my downloads folder to see if it would work, and it still didn’t. So I then removed my entire Sims 2 folder from my documents folder so the game could create a new one. The game is loading now, however when I place my downloads folder back in, none of my CC in buy mode is showing up. I’ve followed the instructions in this post (http://modthesims.info/t/312603 ) to help me out (which has worked before) but each time I put my downloads folder back in the game does not load. (I have the Ultimate Collection btw) Can anyone help me out?

If you created a new game, you'll have to enable CC again.

But it is enabled. Everything else is showing up fine except for the objects in buy mode.

Try downloading and installing a new copy of the CEP. It can't do any harm.

Assuming that you have all the meshes...and I assume you do if it's a lot of stuff...Do you get that screen when you've loaded the game that "warns" about custom content being detected? If not -- and you've not deliberately done anything to bypass that screen -- you may need to re-enable. Do build-mode objects, if you have any, show in the catalog? Or are you just talking about Bodyshop/CAS stuff when you say "everything else?" IIRC, Bodyshop stuff doesn't need to have CC enabled to show/work, only build/buy and mods. (I could be wrong about that, though; it's been so long since I had to figure out CC-enabling and didn't just do it by rote when installing on a new machine.)

Yes, Bodyshop/CAS stuff and build mode objects show up. Every time the game creates a new documents folder, I make sure all the settings I had before are set again before even doing anything else, including enabling CC and disabling the CC dialogue since that seems to work for me.

Check that your antivirus program is not performing an on-access scan of your CC files as the game loads. I would add Documents/ EA Games to the exclusions list. If there's a file lock already on the folders when the game tries to read them, the CC won't be loaded. That's the only thing I can think of that would cause one particular subset of your CC not to work (barring file damage).

I was gonna post pretty much exactly what Simsample did. But I'll add making sure that you do, indeed, have the meshes, that you didn't accidentally remove/delete a whole folder of 'em or something. Because now you're down to corrupt files/folders, missing meshes, or an overzealous antivirus.

there is a separate setting for mods/hacks; through a dialog box. dialog box would list all mods/hacks in game and would have option to either enable or disable.
the asterisk icon in "Game Settings" would bring up that dialog box.

So I attempted to try this along with completely uninstalling and re-installing the game and unfortunately nothing has worked. I'll have to try simsample's suggestion but other than that I'm not sure what else to do at this point.

As I said, it can't do any harm - it is only supposed to work for maxi objects - but you need a new one with a new re-install in any case, so now that is at least done.
Please don't uninstall and reinstall the UC all the time - it is not needed.
Be careful of using cc or registry cleaners as well - some of them delete some of the .dll files the game needs to run properly.