Hi @Raheem Anderson ,
Under normal circumstances, this will only happen if the Azure AD user is deleted.
1.Please check M365 Admin center, whether the account is in Active Users or Deleted Users.
2.Have you checked whether the user has been deleted through the Audit log? If not, you can check to see if there is a delete record.
Go to https://compliance.microsoft.com and sign in. In the left pane of the compliance portal, select Audit.
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