Illuminate\Broadcasting\BroadcastException: auth_key should be a valid app key laravel 5.8

I am integration laravel pusher it is working fine on local host but on live server in queue it is giving this error

Illuminate\Broadcasting\BroadcastException: auth_key should be a valid app key 

env file

BROADCAST_DRIVER=pusher
PUSHER_APP_ID=*****
PUSHER_APP_KEY=****
PUSHER_APP_SECRET=*****
PUSHER_APP_CLUSTER=ap2

broadcating.php

  'pusher' => [
            'driver' => 'pusher',
            'key' => env('PUSHER_APP_KEY'),
            'secret' => env('PUSHER_APP_SECRET'),
            'app_id' => env('PUSHER_APP_ID'),
            'options' => [
                'cluster' => 'ap2',
                'useTLS' => true,
            ],
        ],

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