Fix OneDrive Guest User Cannot Sync Shared Folder Permission Error
Question details
Guest users are unable to sync a shared OneDrive folder using the desktop sync client despite being able to access it via a web browser.
- Product
- Microsoft OneDrive
- Device & OS
- not provided
- Scenario
- A guest user from another Microsoft 365 tenant attempts to locally sync a shared folder using the OneDrive client.
- Observed behavior
- The user receives an error message stating "You don't have permission to sync this library" when initiating the sync.
Ensure you have administrator access to both the Microsoft 365 tenant and Microsoft Entra ID (Azure AD), as resolving cross-tenant B2B sync restrictions requires checking organizational policies.
Review Azure AD Conditional Access Policies
Cross-tenant B2B sync has strict policy requirements that must be configured to allow external desktop client access.
B2B sync utilizes different authentication restrictions compared to internal-user sync. If conditional access policies block non-managed devices or specific client apps for external users, the sync client will throw a permission error even if browser access works.
Log in to the Microsoft Entra admin center with global administrator credentials.
Navigate to the Conditional Access policies section and review any policies applying to Guest or external users.
Ensure these policies are compatible with external B2B sync access according to Microsoft's official B2B sync guidelines, ensuring desktop apps are not inadvertently blocked.
Remove and Re-invite the Guest Account
Re-provisioning the guest account can fix corrupted permissions or caching issues within the directory.
Test with an Alternate Tenant and Contact Support
Isolate whether the sync issue is specific to the guest's home tenant or your tenant's configuration.
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Frequently Asked Questions
Why can guest users view the OneDrive folder in a browser but not sync it?
Browser access and desktop client syncing use different authentication protocols. B2B sync through the OneDrive desktop client is subjected to stricter Azure AD Conditional Access and device management policies that may block desktop applications while allowing web traffic.
Do guest users need a specific OneDrive client version to sync B2B shared folders?
Yes, guest users must ensure they are using the latest version of the OneDrive sync app. They also need to ensure they are signed into the client with the exact same account email that received the shared folder invitation.
Can B2B cross-tenant sync be completely disabled by an administrator?
Yes, tenant administrators can globally disable B2B sync in the SharePoint admin center or via Microsoft Entra ID cross-tenant access settings. If disabled, any guest trying to use the sync client will receive a permission error.
