A (growing) collection of tools and techniques for debugging your Webpack(er) setup.
I highly recommend reading the SurviveJS - Webpack 5 ebook for a real deep dive!.
Locating the Issue
Use the network tab in your browser to view the CSS that’s being sent to the browser for clues.
Cached Styles
If you update your styles but your UI does not change and there are no errors, it’s likely browser caching.
Hard reload after clearing your cache and you should see your changes.
To avoid these errors, import your styles into your JS pack vs. using style-loader.