Product: Programmable SMS
The WhatsApp message you are attempting to send uses a "Marketing" category template and the user you are trying to reach has opted out from receiving your marketing messages.
Recipient has opted out of WhatsApp marketing messages from your business.
The user needs to opt back into WhatsApp marketing messages from your business. You may still send templated WhatsApp messages of other categories, such as Authentication and Utility, to this user.