Problem Description
A SharePoint Online restore job may fail with an internal error when performing an in-place restore or restore-as-a-copy at the site or subsite level. The error typically occurs when Insync attempts to create a new subsite under a SharePoint site, but subsite creation is disabled in the tenant settings.
Cause
This issue arises because Microsoft has deprecated subsite creation in SharePoint Online for many tenants as part of modernization and governance policies.
If the Enable Subsite Creation setting is turned off, any request to create a subsite will fail with an error from SharePoint.
inSync needs this capability for restoring entire sites or creating subsites during restore-as-a-copy operations.
Error Snippet / Logs
A typical error message in restore logs:
1 Error while creating site: Internal error. Response Code: 400
2 Text: {"error":{"code":"-1, System.InvalidOperationException","message":{"value":"New subsites are not available for your organization. Create a new site instead."}}}
Restore Summary often shows:
Subsites: Failed
Document Libraries, Folders, Files: May succeed partially or entirely
Resolution
Two approaches can resolve this issue:
Option 1: Restore at Folder or Document Library Level
If subsite creation cannot be enabled, select specific document libraries or folders for restore instead of restoring the whole site or using restore-as-a-copy.
This method avoids the need for subsite creation.
Option 2: Enable Subsite Creation (If Organizational Policy Allows)
Ensure you have SharePoint Online Management Shell installed.
Connect to your SharePoint Online admin center:
Enable subsite creation:
Confirm the setting:
Retry the restore job. Disable the setting again if required by policy.
❗ Important Notes
For permanent compliance with Microsoft guidance, use modern site collections rather than subsites.
If your tenant policies do not allow enabling subsite creation, Folder-level restore is the only supported workaround.