When a message fails, it can fall into two categories: Undeliverable or Bounced.
What does Undeliverable mean?
A message is Undeliverable when WhatsApp cannot deliver it at all. This usually happens if :
The phone number is not registered on WhatsApp.
The recipient has not accepted WhastApp Terms of Service and Privacy Policy.
The recipient is using an old WhastApp version.
What does Bounced mean?
A message is Bounced when WhatsApp attempted delivery but the message could not reach the recipient. Common reasons include:
The recipient has no internet connection (no data or Wi-Fi).
The phone is switched off or out of network coverage.
WhatsApp notifications are delayed or disabled.
The recipient has blocked your number.