VRC SDK 3.0 Not Uploading in Unity

I’ve been working on an avatar I purchased for a friend and have not been able to upload it on Desktop or Quest after numerous attempts. It will create a prefab in the assets & attach an id, but stop there. The closest I have come to solving this was a popup error regarding a script, of which I have no idea what to do with. Does anyone have an idea for how to fix this? Thanks!