Unknown subscribers may sometimes appear in your Audience. They look like subscribers without any information about them.
Why did they appear?
Probably, because of some problem with the connection between Facebook and your bot. Those subscribers are real users, too, just like any other subscriber - but we haven't received the information about them from Facebook.
What was the problem?
Usually, this happens if something has been changed in the settings of the Facebook page concerning access to it: the password, country or age restrictions, admin roles, and permissions.
How can I fix it?
Quick and simple! Refresh Permissions using the button here:
When will it work?
Permissions are refreshed immediately, but for Unknown Subscribers, it'll take time to receive the info from Facebook and refresh their profiles.
It will be completed either when the user interacts with your bot or automatically over an indefinite period of time. Don't worry, sooner or later it will happen!