Occasionally, a phone number may show one of two particular statuses that are related to quality and messaging limits: Flagged and Restricted.
Flagged
This is a warned state. When the quality rating reaches a low (red) state, the phone number is moved to a Flagged status. During this period, we would like to recommend you to on-hold the broadcast attempt to maintain your tier and quality. If your WABA got flagged and not getting better within a week, your tier might drop to the lower level.
Restricted
Phone numbers that reach their messaging limit are moved to a Restricted state. During a Restricted state, the number will be unable to send any notification messages until the 24-hour window for sending messages is reset. Mostly, an error response will appear like this if the number sends a message
Note : The message failed to send because there are restrictions on how many messages can be sent from this phone number. This may be because too many previous messages were blocked or flagged as spam.
To maintain high quality
The Quality Rating is based on user feedback and we are not able to see exactly the details.
Make sure messages follow the WhatsApp Business Policy.
Only send messages to users who have opted in to receive messages from your business.
Make the messages highly personalized and useful to users. Avoid sending open-ended welcome or introductory messages.
Be mindful of messaging frequency; avoid sending customers too many messages a day. Be thoughtful of informational messages, optimizing for content and length
Note : You can wait for 24 hours since you got flagged status to improve the quality rating, then your number will return to connected status.