For WhatsApp, the message is undeliverable due to the recipient being an invalid user on WhatsApp or other Meta restrictions for WhatsApp.
Possible Causes
For WhatsApp, reasons can include:
Recipient phone number is not a WhatsApp phone number.
Recipient has not accepted WhatsApp's new Terms of Service and Privacy Policy.
Recipient is using an old, unsupported version of the WhatsApp client for their phone.
Meta blocked the delivery of Marketing template messages to the recipient. Meta imposes an unspecified limit to how many marketing messages WhatsApp users can receive at a given time. This limit is based on the number of marketing conversations opened with a user from any business, and is not related to the interactions between the user and your business.
Possible Solutions
Confirm with the recipient that they have accepted Meta's latest Terms of Service for WhatsApp. If they have not, then send them this link
https://wa.me/tos/20210210
to accept the latest WhatsApp Terms of Service.
Confirm with the recipient that they have an active WhatsApp phone number on the latest client version for their phone.