Postcss error when yarn serve.

[Scraayp]

When trying to run the project with yarn serve. I get this error.

 error  in ./src/styles/global.scss

Syntax Error: Error: PostCSS received undefined instead of CSS string


 @ ./src/styles/global.scss 4:14-256 15:3-20:5 16:22-264
 @ ./src/main.js
 @ multi (webpack)-dev-server/client?http://192.168.2.100:8080&sockPath=/sockjs-node (webpack)/hot/dev-server.js ./src/main.js