Fetch request returns 422 error - 'value is not a valid dict'

Question

I am trying to send a post request to my api, however I am getting a 422 response. In insomnia, using the exact same body and everything, I am able to successfully make the request, so I am unsure why my code doesn't do the exact same.

    const[stopinfo, setStopInfo] = useState([]);

const requestOptions = {
    method: 'POST',
    body: JSON.stringify({ 
        'min_date': startDate,
        'max_date': endDate,
        'min_time': '00:00:00',
        'max_time': '23:00:00',
        'bus_ids': [2,3,4],
        'route_ids': [1,2,3]
     })
};

const fetchStopData = async () => {
fetch("https://mywebsite.com/api/data/stopinfo", requestOptions).then(response => response.json())
.then(data => setStopInfo(data))
    }

useEffect(() => {
    fetchStopData()
  },[]);