Generate your Whatsapp API on Sendapp Colud
Log in or register on https://app.sendapp.cloud and create an instance with your WhatsApp Business or Personal multisession account.
After creating the instance you can copy your Token and your Isatnza ID to paste it in the Shopify webhook configurator https://shopify.sendapp.live/generate.php

Message configuration 

Go to the webhook configuration https://shopify.sendapp.live/generate.php to customize the notification messages you want to send to your customers. If you want to modify the messages of an already existing account after entering your token and the instance, press the EDIT key, your notifications to be modified will appear. In the Whatsapp Phone Number for Admin notification field you must enter a WhatsApp phone number including the international prefix without any sign, dash or parenthesis. On this number you will receive notifications as an administrator. When you have finished customizing you have to click the "GENERATE URL FOR SHOPIFY" button, the custom url will appear to be entered in your Shopify administration.

Shopify Notifications Setup

Log in to your Shopfy administration, go to Settings / Notifications at the end of this page you will find the section Webhook
click the "Create Webhook" button. Select from the events "Order Update", Format "JSON",
paste the Sendapp url in the URL field, select Webhook API version 2022-4 (Latest) from the menu.
To confirm the sending of notifications you have to click the Save button and you are immediately ready to send WhatsApp notifications from your Store.