Okay, so apparently the problem was BitDefender. I didn’t think it could be a problem because I disabled it, but when I uninstalled it (which actually required downloading an uninstall tool from their website), The Sims 4 launched with vorpX. Thanks so much!
I don’t think there’s a program interfering, because Portal 2 launches with vorpX easily. But I disabled all my malware protection, Discord, anything that could be interfering and still nothing.
Is there another way to install a hook helper? The Sims 4 doesn’t even get the “attaching to” dialogue, it just launches normally without anything out of the ordinary happening. Once I’m in-game, the vorpX menu hotkey has no effect and my VR headset still shows my SteamVR home.