This is a little something I've noticed and although it's not a deal-breaker, it's certainly bothering me. A few base game items, as well as some CC ones are simply not available in the catalog to buy. One absent base object is the "On a Pedestal by Yucan Byall" sculpture that has vanished, as well as some Maxis Exchange items which won't appear in game, such as the Alienware PC and the egg stereo I've recently installed.

These are the ones I managed to spot, but I'm willing to bet there might be more missing stuff that I just haven't noticed. Is this something that is known to happen? I've read in other threads about anti-virus interfering in ts2 game files, but I'm not sure if this is my case, as I only got windows defender and it's only affecting very specific objects. I do have a TON of CC, mostly CAS but a considerable Build/Buy chunk, and I don't know if any of those can hide or conflict with base game objects.

How could I go about troubleshooting this?

P.S.: I have all EPs and SPs (Not UC).

A lot of EA bullcrap because they never updated it for later EP's.
One I can thing of off my head is this one https://modthesims.info/d/209407/ma...d-for-pets.html
There are more but for the life of me I don't remember where there at.

Most likely, you have some CC that is using the same ID as the Maxis items, and so overriding it.
Backup your neighbourhoods and then test without any CC (refresh your caches). Do the items show up?