in your code you dont have a **channel **which notification can work with us code
e.g.
private fun showNotification() {
val builder = NotificationCompat.Builder(this, NOTIFICATION_CHANNEL_ID)
builder.setContentTitle("")
builder.setContentText("")
builder.setSmallIcon()
val notification = builder.build()
val manager = NotificationManagerCompat.from(this)
manager.notify(1, notification)
}
companion object {
const val NOTIFICATION_CHANNEL_ID = "my_channel_id_01"
}
in this moment you can just add const NOTIFICATION_CHANNEL_ID and your code does work