What else do I need to download for the Elizabeth succubus outfit? Tried loading it and got the red error signs
It was never formally released, so your best bet would be grabbing the most recent Content Dump and seeing if it's in there.
Honestly I'm not sure how you managed to get the Outfit Loader file for it (I assume that's what you mean by trying to load it). It must have gotten automatically scooped up in one of my outfit releases.