BroadcastException 404 NOT FOUND in PusherBroadcaster.php (line 106)

First time I've ever posted here for laravel help! I'm trying to get Broadcast events working on Laravel 5.4 with pusher

When I set the broadcast driver to 'log' I am successfully getting the details in the log so I know most things are working. However its the broadcasting that is the issue. When i set things to pusher I am getting a 404 File not found exception

BroadcastException

404 NOT FOUND

in PusherBroadcaster.php (line 106)

I have

"pusher/pusher-php-server": "^2.6", in the composer.json

and all the keys etc are in the .env file

The method being called in PusherBroadcaster.php is

` public function broadcast(array $channels, $event, array $payload = []) { $socket = Arr::pull($payload, 'socket');

      $response = $this->pusher->trigger(
          $this->formatChannels($channels), $event, $payload, $socket, true
      );

     if ((is_array($response) && $response['status'] >= 200 && $response['status'] <= 299)
        || $response === true) {
         return;
     }

     throw new BroadcastException(                                                                                                   
         is_bool($response) ? 'Failed to connect to Pusher.' : $response['body']
     );
 }`

and its the response['body'] which has the "404 FILE NOT FOUND" response so it looks like its something to do with connecting to pusher

This is my first broadcast with pusher so Im a newb as far as this is concerned.

Help ;-)