Note:
Due to their privacy and policy, WhatsApp (Meta) will not disclose the exact causes of these errors.

Common errors thrown by WhatsApp

1. Unknown error (Failed reason: Unknown error) – This error is thrown when WhatsApp faces an unexpected issue while trying to process your message. You may wait for some time and try sending your message later.
   
2. Recipient not valid for this integration service (Failed reason: Invalid recipient) – If the recipient is an invalid user on WhatsApp, you will receive this error. Some of the reasons why WhatsApp identifies the recipients as invalid include:
   (a) The recipient's phone number might be invalid on WhatsApp. You can recheck the recipient's phone number and try sending the message again.
   (b) WhatsApp (Meta) might have blocked your message from reaching the recipient. This could be because the recipient might have already received too many marketing messages from various businesses, reaching their limit to receive marketing messages via WhatsApp. Learn more about Per-User Marketing Template Message Limits.
   (c) The recipient has not accepted WhatsApp's new Terms of Service and Privacy Policy.
   (d) The recipient is using an old WhatsApp version. They must use any of these WhatsApp version or greater – Android: 2.21.15.15, SMBA: 2.21.15.15, iOS: 2.21.170.4, SMBI:2.21.170.4, KaiOS: 2.2130.10, or Web: 2.2132.6.
3. Recipient isn't receiving messages from you right now (Failed reason: Blocked by recipient) – You'll get this error if the recipient has blocked the number you are currently using to send WhatsApp messages.
   
4. Recipient under integration experiment (Failed reason: Experiment in progress) – WhatsApp is running an experiment where 1% of users will not receive any marketing messages from businesses unless a chat already exists between them. You’ll face this error if you try to send messages to such users. You can reach out to them outside WhatsApp and ask them to initiate a WhatsApp chat with you so you can resend the message to them.
   
5. Integration Service Rate limit exceed (Failed reason: Sending limit exceeded) – You'll get this error if you've exceeded the WhatsApp sending limit.
   
6. Marketing Template Limit Exceeded (Failed reason: Marketing template limit exceeded) – Unable to send this message because WhatsApp might restrict the number of marketing template messages a user can receive from a business within a certain period of time. Initially, this affects messages that are less likely to be read. Soon, fewer marketing conversations will be delivered to users who are less likely to engage with them. WhatsApp’s help documentation suggests that if you encounter this error, it is ideal to refrain from immediately sending further messages. This could lead to another error as the limit might still be in place. You can attempt to send the messages again, by gradually increasing the time gap, until all messages are successfully delivered. Learn more about WhatsApp’s Per-User Marketing Template Message Limits
   
7. Marketing template paused for US numbers (Failed reason: User marketing template limit) – Unable to send the message as starting from April 1, 2025, WhatsApp (Meta) has decided to temporarily pause the delivery of any marketing template messages to customers with US phone numbers (+1 calling code and US area codes). Learn more

Possible solutions

1. Through a non-WhatsApp mode of communication, ask your recipient to confirm that you are not on their blocked list.
   
2. Ensure that your recipients have accepted WhatsApp's new Terms of Service and Privacy Policy.
   
3. Confirm that your recipients are using an updated version of WhatsApp.
   
4. Verify that your recipients can send a message to your WhatsApp business phone number.
   
5. Keep a track of your WhatsApp message sending limits. 

Related help documents

1. Best practices for WhatsApp campaign
   
2. Message limits and Quality rating