If you experience an error that a student or group cannot be found, it may have been due to the student or group not being added properly. Class Notebook works in coordination with Office 365 users and groups to provision the permissions to sections within the Notebook.
Be certain to add students or groups correctly. As well, be aware that renaming users and groups in O365 can impact the students or groups you see within Class Notebook.
When using a OneNote Class/Staff Notebook created via Microsoft Teams, you cannot add/remove Students or members using the Class Notebook Wizard online.
Notebook members must be added/removed via Microsoft Teams.