Avatar Custom Shaders not workiong

I'm trying to tune the meta avatar shading. I'm following the docs on how to use custom shaders, but except for the horizon and khronos examples, all shaders have this issue where the avatar does not seem to get animated. It just sits sideways. I think I have things setup correctly (horizon shader works fine) but as soon as I apply my own shader and material, the avatar does not get tracked/animated and lays sideways: 

Does the avatar material/shader need some special flag? The docs don't mention any of that. I'm using Unity URP on an LTS version.

Any help is appreciated.