Theme inheritance not working

I'm trying to inherit from a theme so I can change the sidebar text without messing with the base theme, as suggested by the docs. While I'm able to modify the template files just fine, and have them show up on the site, none of the css is working right. It's all just default html. What can I do to make the css work right?

Check the CSS links point to the correct URL, to start with. Is there any error in the browser console?

I have checked the page source, and the parent themes css is not linked. What could be the cause of this?

You need to post more information. Do you have your own base twig template now? If so, the original one is overridden.

Right sorry. The only two files I have overridden are a partial and item.html.twig. And before anyone asks, this issue occurs regardless of the base theme.

Does the theme use Sass? Are you compiling it? What command are you using?

The theme is using sass, however I am just relying on the default compiled css (in other words, I'm not compiling sass at all). But even then, the base theme can still find the compiled css if I use it directly, only the sub theme is having the issue.