Permission & Access Issues

How to Fix External Users Cannot Access SharePoint Site or Subsites

Maira Mehtab Sep 20, 2026 869 views

Question details

External users and specific partner guest accounts are receiving an 'Unknown issue' error when attempting to access a previously available SharePoint site or its subsites.

Product: Microsoft SharePoint
Device & OS: not provided
Scenario: A tenant administrator is trying to allow external partners and specific GDAP-related guest users to access and collaborate on a SharePoint site, but they are blocked by an unexpected error.
Observed behavior: External users are unable to access the site and receive an 'Unknown issue' error. In some cases, general external users regain access after adjustments, but specific managed guest accounts remain blocked.

Before you start

Before troubleshooting, ensure you have SharePoint Administrator or Global Administrator privileges to review and modify tenant-level external sharing settings and GDAP relationships.

Solution 1Recommended

Verify SharePoint External Sharing and Tenant Settings

Check both the site-level permissions and the organization-wide external collaboration settings to ensure guest access is explicitly allowed.

SharePoint requires both the organization-level and the site-level sharing settings to permit external users. If the tenant settings are more restrictive than the site settings, the external user will be blocked with an error.

Check Site-Level External Sharing

Navigate to the SharePoint admin center, expand 'Sites', and click 'Active sites'. Select the affected site, click the 'Policies' tab, and under 'External sharing', ensure it is set to 'New and existing guests'.

Review Tenant-Level Sharing Settings

In the SharePoint admin center, go to 'Policies' > 'Sharing' in the left navigation pane. Confirm that the external sharing slider for SharePoint is set to 'New and existing guests' or 'Anyone'.

Verify Azure AD External Collaboration Settings

Open the Microsoft Entra admin center (Azure AD), navigate to 'External Identities' > 'External collaboration settings', and ensure that guest user access is not restricted by default policies.

Propagation Time: Changes to tenant-level external sharing policies may take up to an hour to fully propagate across all SharePoint sites and subsites.

Solution 2

Investigate GDAP Roles and Cross-Tenant Configurations

If general external users can access the site but specific managed partners (e.g., GDAP relationships) cannot, you must inspect the delegated admin privileges.

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Frequently Asked Questions

Why am I getting an 'Unknown issue' error when accessing a SharePoint site as a guest?

This error typically indicates a conflict in tenant-level external sharing settings, a misconfigured Conditional Access policy in Azure AD, or an expired guest invitation that prevents proper authentication.

What is a GDAP relationship in Office 365?

Granular Delegated Admin Privileges (GDAP) is a security feature that provides partners with least-privileged, time-bound access to a customer's tenant. If the correct roles are not assigned, partner guest accounts may be blocked from accessing resources like SharePoint.

How do I enable external sharing for a specific SharePoint site?

As a SharePoint admin, go to the SharePoint admin center, select 'Active sites', click on your desired site, navigate to the 'Policies' tab, click 'External sharing', and select 'New and existing guests'.

Can external users access a SharePoint subsite if the parent site restricts them?

No. Subsites generally inherit permissions from the parent site. If the parent site or the global tenant settings restrict external sharing, guest users will not be able to access the subsite, even if you try to share it directly.

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