While chatting with Messenger customers in your inbox you might notice the following warning in your chat window:
This is because MobileMonkey utilizes the human-agent tag for all messages sent from MM inbox. This tag allows us to bypass Facebook's 24 hour restriction and is meant to be used only for customer support inquires. When using this tag, Facebook requires that messages be sent within 7 days from the last time the user messaged your page.
If you are responding to a customer inquiry on an issue that has spanned past 7 days, you can send a response directly from Facebook Messenger to bypass this error. Make sure the message you send is for customer support and not promotional in nature. Facebook reserves to right to ban your page if it detects any violation to its messaging policies.
Read more about the 24hr policy here.
Note that there are no formal restrictions for SMS or Webchat contacts, as long as they are still opted in.