Why does my attributes object work in React but not in Next fetchContent?

took an attributes object that worked fine with useContent in a plain React app and moved it into a Next server fetchContent call. the values are just not being applied, no error, the slot renders as if i passed nothing.

here is the call:

const {content} = await fetchContent('home-hero', {  fallback: {...},  attributes: {plan: 'pro'},});

what am i passing wrong here