A Microsoft file hosting and synchronization service.
Typically, Microsoft for education accounts login via what Microsoft calls "Work or School Account" and typically logs in with your university email xxx @ yyy.edu.zz, where as personal M365 accounts typically login with xxx @ outlook.com or hotmail.com.
As the university typically uses a paid license, once a student graduates, the account is withdrawn and the license is then assigned to an new enrolling student.
If you have graduated, then likely this has happened, and it is unlikely you will be able to able to gain back the lost information. You can contact your university for a second opinion.
Warm Regards