Facebook Messenger sometimes notifies you that you have "unread messages" even though you have previously read all of your messages, as you may have seen if you often use the service. This might be annoying since it can be hard to determine whether you have fresh communications that need your attention.
Facebook Messenger's unread message notification is often caused by message requests. Message requests are communications you get from individuals who aren't on your Facebook friends list. These messages are often routed into an unnoticeable separate inbox. Facebook Messenger may notify you that you have "unread messages" even if you have previously read all of your other messages if you have a message request.
Open Facebook Messenger and tap on your profile photo in the upper left corner to check for message requests. Any filtered messages will then show up in a section titled "Message Requests" from there. To remove the "unread messages" indicator, be sure to react to any message requests you receive.
Facebook Messenger issues or malfunctions may also cause the app to report that you have unread messages. Like any other software, Facebook Messenger sometimes has technical problems, and these problems might occasionally result in alerts that show improperly. The notice could just be an app bug if you've checked for message requests and don't see any additional unread messages.
Try forcing the app to close and then reopen, or restart your device, to fix this problem. If the problem continues, you may try to make sure you're using the most recent version of Facebook Messenger by checking for updates.
Facebook Messenger's "Mark as Unread" function is a third reason why the program can report that you have unread messages. Even if you've already read a message, you may mark it as "unread" using this feature and return to it later. Facebook Messenger may notify you that you have unread messages even though you have already viewed them if you unintentionally tagged a message as "unread."
Tap and hold on the discussion thread that is showing the "unread messages" indication to check for inadvertently tagged messages. You should then have the choice to designate the chat as "read." You may need to press and hold on each chat thread to see which one has the unintentional "unread" mark if you're unsure which conversation it belongs to.
Finally, there are a number of reasons why Facebook Messenger might report that you have unread messages, including message requests, app bugs, and unintentional use of the "Mark as Unread" feature. You may fix the problem and make sure that you're constantly aware of new messages that need your attention by checking for message requests, force-closing the app or restarting your device, checking for updates, and marking unintentionally tagged messages as "read."