Hi, I'm John! I will help you with this.
Since you didn’t archive your classes yourself, they may have been hidden, automatically archived by an administrator, or there could be a syncing issue with the app. I suggest asking your school's IT or Microsoft 365 administrator, if the classes still don’t show up, it’s possible your school organization made a change on their end.
Let me know if you have any further questions or concerns.
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Regards,
John J.D.