Why can't I reply to a Facebook message in Inbox?
Facebook’s Messenger Platform Policy provides the following reasons for receiving the error message Unable to send Facebook message when replying to a Facebook message in Inbox:
- It has been more than 7 days since the last message was received from the user. Facebook does not allow replies after 7 days.
- The Facebook user blocked or muted your conversation.
For more information, see Facebook’s Messenger Platform Policy Overview.