How to send messages to Chrome Cast

Question

When using react native google cast I'm trying to send a custom message for casting my web page by setting my custom reciver ID in the app.json. But when i connect to the chrome cast it establishes a succesful connection and "sends the message" but nothing gets sent through

import React, { useEffect } from 'react';
import { CastButton, useRemoteMediaClient, useCastChannel } from 'react-native-google-cast';


export default function ChromeCast() {
  const channel = useCastChannel('urn:x-cast:com.url.cast', message => console.log('Received message', message));
  const client = useRemoteMediaClient();

  useEffect(() => {
    const loadReceiverUrl = async () => {
      try {
        if (client && channel) { // Check if both client and channel are available
          //Initial Image before Scoring Page
          await client.loadMedia({
            mediaInfo: {
              contentUrl: 'https://sportyapp.co.za/assets/images/SportyAppLoading.png',
            }
          });
          // Send message to the channel
          if (client && channel.sendMessage) {
            
            channel.sendMessage({
              "media": {
                "contentId": "body",
                "contentUrl": "https://sportyapp.co.za/scoreapi.php?view=tv&layout=99&stream_url=0a897bf3-377e-5bfd-8f4e-a70bdf23cdf7.local&target=0a897bf3-377e-5bfd-8f4e-a70bdf23cdf7.local",
              },
              "credentials": "SportScreen"
            });
            console.log('Message sent');
          } else {
            console.error('sendMessage method is not available on the channel object.');
          }
        }
      } catch (error) {
        console.error('Error loading custom receiver URL:', error);
      }
    };

    loadReceiverUrl();
    
    return () => {
      // Clean up any resources if needed
    };
  }, [client, channel]);

  return <CastButton style={{ width: 24, height: 24, tintColor: 'blue', marginRight: 20 }} />;
}

So ive tried teh following but when it runs it just comes with a blacnk screen with the cast logo in the middle, im guessing indicating there is no media that has been loaded but before that it shows a progress bar that loads up to 50% and then goes away to a blank no content screen