You do not have the necessary permission for the specified Page to perform the requested action.
If you’re receiving this message when you have been made an admin of a facebook page or are the owner of a facebook page (only when you attempt to access the messages or messenger) and you can’t figure out why here was the thing that solved the issue for me.
If the facebook page you’re trying to access has 2-factor verification you have to set up 2-factor verification on your own personal profile and in the messenger by using an authenticator app (I used google authenticator). This should resolve the issue.
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