OneDrive backups fail with 503 notAllowed 'Access to this site has been blocked' for archived or unlicensed drives

OneDrive backups fail with 503 notAllowed 'Access to this site has been blocked' for archived or unlicensed drives

Machine-distilled from a resolved support ticket on 2026-09-28. Source ref: 934983c2a94a. Verify before relying on it.

Applies to: HYCU R-Cloud protecting Microsoft 365 OneDrive (version not specified)

Symptom: A subset of OneDrive backups in a Microsoft 365 protection policy start failing, while other OneDrive backups in the same tenant continue to succeed. The error is: Error code: 503 Message: {"error":{"code":"notAllowed","message":"Access to this site has been blocked. Please contact the administrator to resolve this problem."}}. The customer reports no tenant or permission changes.

Cause: The affected OneDrive locations are archived or belong to users who no longer have a Microsoft 365 licence. Microsoft blocks access to these drives, so HYCU cannot reach them through the Microsoft Graph API, even with application-level permissions in place. This is not caused by missing HYCU or tenant permissions: a permissions problem would normally affect all backups, not a subset.

Resolution: 1. Compare the list of failing OneDrive backup entities against user licence and archive status in the Microsoft 365 admin centre. 2. Confirm that the failing drives are archived or unlicensed. 3. Exclude those OneDrive entities from the HYCU protection policy so they are no longer scheduled for backup. 4. If any of those drives still need protection, restore the user's licence or unarchive the drive in Microsoft 365 first, then add the drive back to the policy. 5. Do not spend time re-granting Graph permissions or re-authenticating when only a subset of drives fails with this specific notAllowed message. Check licensing and archive state first.