Hello @Chibu this error might indicate an issue with the permissions required to create a class. From the create class documentation, your application requires this permission: EduRoster.ReadWrite.All
. You can check the permissions by clicking on the Access Token tab in Graph Explorer, then click on the {} which will open your token using jwt.ms. From there you can inspect the token and check the scp and confirm that this permission is present. If not, check your application on Azure AD and grant the permission. Please note that EduRoster.ReadWrite.All requires admin consent
Let me know if this helps and if you have further questions,
Diana.