Guest access stopped working for SharePoint sites using classic experience

Question

Two days ago, we began to receive reports from our guest users indicating "Access Denied" to the folders and documents that we shared with them. In our tenant, we do not register guest users, we have explicitly allowed users to share with guest from certain folders. The authentication flow consisted of user getting a link, typing their email address and getting a OPT Code. Sometime around Tuesday afternoon, something broke and users get access denied all the time even after successfully entering codes.

Our tenant and site settings allow access for current and new guest nothing was changed on our end.

We have tried to re-send links, re-share folders, create new folders and nothing works.

We noticed during our testing that the sites which are failing were created with classic templates 2 to 4 years back.

OneDrive and New Sites which were created under newer templates or associated to Teams sites work fine for guests.

Microsoft support have not found any root cause for this, they have not determined if this is a bug recently introduced.

Has anyone encountered a similar issue?

Answer 1

Dear @Cristobal Fallas,

Thank you for contacting us regarding the sudden "Access Denied" issues experienced by your guest users when accessing content shared from your classic SharePoint sites. We understand this is a critical issue impacting your external collaboration, especially since the modern sites (OneDrive and Teams-associated sites) are functioning correctly. 

While your description focuses on guest access failures on classic sites, we have identified a Service Health Incident that may be related to broader access and sharing failures within SharePoint Online, potentially affecting how permissions are processed: 

We are aware of an ongoing issue impacting access to some Microsoft 365 services. 

• Issue ID: SP1177145
• Status: Service Degradation 
• Start Time: Oct 14, 2025, 1:50 AM GMT+7

You can access this incident tracking through Microsoft 365 admin center > Service Health (accessible as an IT admin or global admin)

What’s Happening? 

Some users with edit and full control permissions, including guest users, may be unable to access or share files, folders, or list items in SharePoint Online. This issue specifically affects items that were deleted and recently restored from the recycle bin.

Root Cause: 

Microsoft has identified that a recent deployment introduced a code regression, causing compatibility issues with restored items.

Current Status: 

As of November 6, 2025, Microsoft is still working to address additional errors discovered during the validation of their fix. A timeline for full deployment will be provided once available. The next update is scheduled for Thursday, November 13, 2025, at 3:00 AM GMT+7.

What You Can Do: 

• Avoid sharing items that were recently restored from the recycle bin.
• Use modern SharePoint sites or OneDrive for guest sharing, as these are not affected.
• If critical, consider raising a support case with Microsoft to manually apply the fix to affected items.

We apologize for any disruption this may cause and appreciate your patience as we work toward a resolution. We will keep you updated as new information becomes available.

Should you need further assistance, please don’t hesitate to contact.

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