If you created your macro in the CSS file and now moved it elsewhere, make sure you are importing the macro with a reference name then be sure to prefix any calls to the function with the name.
I like to import the file as "macros".
{% import 'path/to-your/macros.html' as macros %}
Example usage would then be:
.ctaButton {
{{macros.borderradius(params)}}
}
Your error is usually because you try referencing a macro that's in the same html file (or css) that you're working on.