This article will help you understand the various status notifications that WhatsApp Business API sends for the status of the messages between you and your users
For each message, get notified when the message has been sent, delivered, read and/or deleted. If the message fails to send or isn’t delivered, you get a failed status notification.
The order of these notifications in your app may not reflect the actual timing of the message status. View the timestamp to determine the timing, if necessary.
Note: For a status to be read, it must have been delivered. In some scenarios, such as when a user is in the chat screen and a message arrives, the message is delivered and read almost simultaneously. In this or other similar scenarios, the delivered notification will not be sent back, as it is implied that a message has been delivered if it has been read.