"Spine hierarchy incorrect." but can't find rig panel

[CMYK8964]

I'm trying to convert my own VRM model into a VRChat avatar. I do exactly as indicated by all the tutorials, but when it comes time to upload the avatar to VRChat, I get this error:

Spine hierarchy incorrect. Make sure that the parent of both Shoulders and the Neck is the Chest (or UpperChest if set).

Now, here is where the tutorials assume that I have a toolbar that says "Model | Rig | Animation | Materials", which I don't. I looked at everything and it's not there. I have the latest versions of all the required plugins, too.

Has anyone else encountered this issue? Better yet, has anyone else resolved this issue and found out how to help?