My API GET request is working in Postman, but not in React.JS / the browser.

This is the code I tried simply copied it from postman

useEffect(() => {
    const myHeaders = new Headers();
    myHeaders.append("Amelia", "XldbLuwlIl9rZ4BdGBRlowmkm21e0Bfy9eEzr6OKMM9D");

    const requestOptions = {
      method: "GET",
      headers: myHeaders,
      redirect: "follow",
    };

    fetch(
      "https://staging.terminister.de/wp-admin/admin-ajax.php?action=wpamelia_api&call=/api/v1/appointments",
      requestOptions
    )
      .then((response) => response.json())
      .then((result) => console.log(result))
      .catch((error) => console.error(error));
  }, []);
  }, []);

This is postman’s screenshot enter image description here

Anyone know how to resolve this.