Laravel Echo does not received message from channel

i stuck very bad . in realtime laravel(version 9) project using pusher for websocket. backend can get message but problem is Echo does not received message which sent from backend ...

Event :

class MessageSent implements ShouldBroadcast
{
    use Dispatchable, InteractsWithSockets, SerializesModels;

    public $message ;
    public function __construct($message){
        $this->message=$message;
    }

    public function broadcastOn()
    {
        \Log::debug("{$this->message}");
        return new Channel('chat');
    }

    public function broadcatAs(){
        return 'chat';
    }
}

JS :

 Echo.channel('.chat').listen('MessageSent', (e) => {
        alert(e.message)
    });

further information :

1- according to Event i can log message to laravel.log file which means message sent from frontend to backend .

2-there is no error in console area

3-3-see debug console of pusher official site debug console -> https://i.stack.imgur.com/57dV3.png