Actually, you only have to use the “FeaturesMetadata” label in the contents of the Material Instance. It was previously labeled “Layer 4” in your screenshot, which is why the metadata styling layer wasn’t applying. It’s perfectly acceptable to use arbitrary names for the Material Instances / Layers themselves. See this example:
Sometimes your changes won’t show up until you save the material, or manually click “Apply” in the toolbar. It can be flaky 
In the future, try to verify that your changes were actually applied to the material. And in any case, I’m glad you were able to solve your problem!