FluentUI NorthStar Issue 19476

First, yarn install.

Develop Mode

Run Gatsby in Develop Mode

yarn run develop

And then open http://localhost:8000, you can find that css is correct.

Build

Run

yarn run build
yarn run serve

And open http://localhost:9000, you can see css is missing, all component doesn't render with style.

Open Developer Tools, in <head> tag, there is a style tag with class ssr-css is empty. This tag is set from gatsby-ssr.js, it doesn't render any css into it.