Session errors can occur for several reasons, but they most often occur when WileyPLUS is open in more than one window or tab at a time. I would recommend clearing your cache and cookies (ctrl+shift+delete) in your browser. Once you've done that, completely close the program (IE, Firefox, Chrome, Safari, etc.) and then relaunch it.
Log back into your WileyPLUS course and you should be okay. If not, please come into LIVE CHAT here on our support site and myself or one of my fellow agents can live troubleshoot the issue with you.
Have a great day, and thanks for reaching out!
Tom with Wiley
Senior Technical Support Rep; Community