Notification doesn't vibrate

Question

const val channelId = "notification_channel"
const val channelName = "com.deskmateai.t2chaiwala"
val vibration = longArrayOf(100, 200, 300, 400, 500, 400, 300, 200)

class MyFirebaseMessagingService: FirebaseMessagingService() {
override fun onMessageReceived(remoteMessage: RemoteMessage) {
    super.onMessageReceived(remoteMessage)
    generateNotification(remoteMessage.notification!!.title!!, remoteMessage.notification!!.body!!)

}

// generating notification
private fun generateNotification(title: String, description: String){
    val builder: NotificationCompat.Builder = NotificationCompat.Builder(applicationContext, channelId)
        .setContentTitle(title)
        .setSmallIcon(R.drawable.tea_notify_logo)
        .setAutoCancel(true)
        .setContentText(description)
        .setSound(Settings.System.DEFAULT_NOTIFICATION_URI)
        .setDefaults(NotificationCompat.DEFAULT_VIBRATE)
        .setVibrate(longArrayOf(500, 500))
    val v = applicationContext.getSystemService(Context.VIBRATOR_SERVICE) as Vibrator
    v.vibrate(1000)
    val manager: NotificationManagerCompat = NotificationManagerCompat.from(applicationContext)
    manager.notify(1, builder.build())

    if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.O){
        val channel = NotificationChannel(channelId, channelName, NotificationManager.IMPORTANCE_DEFAULT)
        channel.enableLights(true)
        channel.enableVibration(true)
        channel.vibrationPattern = vibration

        val manager = getSystemService(Context.NOTIFICATION_SERVICE) as NotificationManager
        manager.createNotificationChannel(channel)
        manager.notify(1, builder.build())
    }

}

I am making an app in android for that i have integrated firebaase push notification, but my hone is not vibrating when notification come . I have also added vibration permission in android manifest file. and as you can see in code i have done everything to vibrate my phone on notification but it is not.