You are not logged in
If you get a message that "You are not logged in" it usually means that you have had several sessions open and logged out of one of them. When you then try to do something in another session you get the message.
If you exit a session you should close all open screens and log back in.
It is best when you wish to leave a session is to use the Log Out button rather than using the x at the top right of screen.