Currently, in the file illinois_framework_theme.libraries.yml file, line 6 has a directive to save the compiled SCSS file to the theme's ./css directory. This can cause issues on hosting providers that don't allow write access to the theme files (e.g. Pantheon). Removing that directive will cause the compiler to put the compiled CSS into the site's public directory (/sites/default/files), which hosting providers will allow.
Currently, in the file illinois_framework_theme.libraries.yml file, line 6 has a directive to save the compiled SCSS file to the theme's ./css directory. This can cause issues on hosting providers that don't allow write access to the theme files (e.g. Pantheon). Removing that directive will cause the compiler to put the compiled CSS into the site's public directory (/sites/default/files), which hosting providers will allow.
Link to the line in issue: https://github.com/web-illinois/illinois_framework_theme/blob/6a4371c4765696df2cf46e0ecc64d09ddc7962d4/illinois_framework_theme.libraries.yml#L6