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Office Add-ins known issues

Last updated September 15, 2026

This article provides information about current known issues with Office Add-ins. For more information about common error messages you might encounter, see Troubleshoot user errors with Office Add-ins or contact the add-in developer on the Details + support tab on the add-in's detail page in Microsoft Marketplace.

ISSUE: Office Add-ins deployed as Optional or Available may be missing

Some customers may experience issues where centrally deployed Office Add-ins deployed as Optional or Available are missing across Office clients. In affected cases, previously installed add-ins may no longer appear in the ribbon.

STATUS

Investigating.

DETAILS

Impacted add-ins:

  • CodeTwo
  • Letsignit
  • Other organization-managed Office Add-ins centrally deployed as Optional or Available

Affected platforms and clients:

  • Excel desktop
  • Excel on the web
  • Additional Office clients in some environments

USER IMPACT

Users might experience one or more of the following problems:

  • Add-ins disappearing from the ribbon.
  • Failure to load organization-deployed add-ins.

WORKAROUND

IT Admins should change the deployment type of the affected add-ins to Fixed (Default).

If the problem persists, contact Microsoft Support and include diagnostic information such as session IDs, correlation IDs, logs, or network traces where available.

START DATE

Date reported: July 28th, 2026

ISSUE: Users can't find or restore an add-in deployed through optional deployment

When you deploy an Office Add-in by using the optional deployment method, individual users can remove the add-in from the ribbon, and restore it later if they want to use it again. However, there's a regression where in some cases a user can't restore the add-in.

STATUS

Open; tracking ID: ICM21000000950868

IMPACT

Users can't restore an add-in to the ribbon after they remove it. Even if the admin chooses to redeploy the add-in to all users, it might not appear.

WORKAROUND

Create a Microsoft 365 group to implement optional deployment. This workaround works for both XML manifest and unified manifest (JSON) Office Add-ins that are installed in the Integrated apps portal in the Microsoft 365 Admin Center.

  1. Create a Microsoft 365 group for a specific group of users who use the add-in. For more information, see Create a Microsoft 365 group.
    1. Specify a group name such as "My Add-in users".
    2. On the Members page, choose the name of one or more people who are members of the group. These people have optional access to the add-in on their ribbon and can add or remove it.
  2. Go to the Microsoft 365 admin center and update the deployment for the add-in as follows.
    1. Apply to Specific users/groups. Use the name of the Microsoft 365 group you created previously.
    2. Choose the deployment type of Fixed (Default).

When the deployment finishes, anyone in the Microsoft 365 group can remove the add-in from the ribbon by leaving the group. If they want to restore the add-in later, they join the group.

For more information about the previous deployment steps, see:

OUTLOOK ISSUE: Users can't access the My Templates add-in in Exchange Online across all Outlook clients

Users report that the My Templates add-in is missing and undiscoverable across all Outlook surfaces. The add-in subscription exists on affected mailboxes and Centralized Deployment returns it correctly, but client-side discovery within Outlook and Exchange services fails to surface the add-in to end users. Users can't find it in the toolbar, ribbon, Add Apps search, All Apps, Integrated Apps in Admin Center, or via PowerShell Get-App in some cases. The issue presents as a service-side discovery or authentication regression, rather than an admin configuration or Centralized Deployment failure.

STATUS

We're currently working on a fix.

START DATE

Date reported: January 20, 2026

DETAILS

Impacted add-ins: My Templates (primary); Viva Insights (confirmed also impacted as of March 3, 2026); other default add-ins (Bing Maps, Unsubscribe, Common Actions) intermittently affected.

Severity level: High

Affected platforms/clients: Outlook Classic (Desktop, Windows), New Outlook (Desktop, Windows), Outlook on the web, Outlook mobile

USER IMPACT

Widespread, multitenant impact. Impact is tenant-wide in most cases.

CAUSE

Partially identified. Engineering confirmed two contributing factors:

  1. A recent backend change that switched authentication from Exchange Web Services (EWS) to REST for the My Templates add-in caused access errors. The REST auth change was rolled back on March 3, 2026. This change caused a significant drop in errors, but it didn't fully fix the problem. The subscription is present on the mailbox, but add-in information isn't returned to clients.
  2. Historical or recurring root cause: A prior wave was resolved through rollback and cache resets in December 2025, but some tenants never fully recovered.

WORKAROUND (steps to mitigate)

No reliable universal workaround exists. Support teams have tried the following steps with limited or inconsistent success:

  1. Global Admin PowerShell - re-enable the add-in org-wide (the change can take up to 72 hours to reflect; some tenants encounter 401 errors):

    
Set-App -Identity a216ceed-7791-4635-a752-5a4ac0a5eb93 -OrganizationApp -Enabled $true

  2. Verify the add-in status:

    
Get-App -Identity a216ceed-7791-4635-a752-5a4ac0a5eb93

  3. Refresh the Outlook client - In some cases, a page refresh or Outlook restart triggered the add-in to reappear temporarily.

  4. Submit in-app feedback with diagnostic logs - Go to Help > Feedback > Report a Problem in Outlook and share the Session ID and User ID with support so engineering can pull diagnostics.

  5. Reference the public support article - See My Templates are missing from Outlook.

NOTES TO ADMIN

Re-enabling the add-in through PowerShell or the Admin Center doesn't guarantee resolution while the service-side issue is active. Engineering is working on a fix and will post updates to the Service Health Dashboard (SHD).

ISSUE: Intermittent failure to load or deploy Office Add-ins due to Exchange authentication changes

Some users experience problems where Office add-ins fail to load, appear missing, or can't be deployed through the Microsoft 365 admin center. In affected scenarios, admins can see the add-ins in the admin experience or store but they don't render or appear correctly in Outlook or other Office clients.

START DATE

Reported by: Microsoft Support / Customer Reports on: 02/25/2026

DETAILS

Impacted add-ins: Admin-deployed and organization-scoped Office add-ins (including third‑party add-ins)

Severity level: Medium

Current status: Open, mitigation is rolling out.

Affected platforms and clients: Office clients, Microsoft 365 admin center (centralized deployment experience)

USER IMPACT

Intermittent authentication failures cause Office add-ins to appear missing or fail to deploy. This issue primarily affects tenants impacted by recent Exchange Web Services (EWS) security enforcement changes.

CAUSE

As part of ongoing Exchange Web Services (EWS) security improvements, Microsoft enforced stricter authentication requirements that no longer allow certain legacy authentication methods. Some add-in service calls still rely on these legacy paths, causing add-in metadata retrieval requests to be rejected. As a result, affected add-ins can't load or display correctly for users.

WORKAROUND (steps to mitigate)

No customer action is required. Microsoft applied targeted mitigations to restore compatibility while a longer-term fix is validated. Customers who continue to experience issues should contact Microsoft Support for assistance.

SEE ALSO

For more information, see Deprecation of Exchange Web Services (EWS) in Exchange Online.

OUTLOOK ISSUE: Base64-encoded images become corrupted when forwarding messages from a shared mailbox with Cached Exchange Mode turned off

In classic Outlook on Windows, when Cached Exchange Mode is turned off, Base64-encoded images in a message may become corrupted when a user forwards the message from a shared mailbox.

Clients affected: Classic Outlook on Windows

STATUS

We're currently working on a fix.

START DATE

Date reported: November 3, 2025

WORKAROUND

If possible, turn on Cached Exchange Mode when sending emails with Base64-encoded images from a shared mailbox. For guidance, see Turn on Cached Exchange Mode. Alternatively, include the Base64-encoded image as a file attachment instead.

OUTLOOK ISSUE: Users may experience delays of up to ten seconds loading signature add-in images in Exchange Online

STATUS

We've determined that a recent update to an authentication component of attachment logging introduced a regression which is resulting in impact. We're reverting this update to resolve the issue.

Tracking ID: 706911563

IMPACT

Some users may experience delays of up to ten seconds loading images in Exchange Online. This section will be updated as our investigation continues.

START DATE

Monday, November 3, 2025, at 4:31 PM UTC

OUTLOOK ISSUE: Delays loading inline images in email signatures in the new Outlook for Windows and Outlook for the web

We're currently investigating reports from Outlook users who are experiencing loading delays of inline images in email signatures when using the new Outlook for Windows and Outlook for the web. Our findings indicate that this is a server-side performance issue that affects rendering of all inline images. Attempting to send messages while the images are not yet loaded results in the following dialog box.

Outlook images still loading error message.

Tracking ID: 678890927

Client version: 20250822005.18

STATUS

You're still receiving isolated reports from some users about this previously resolved issue. While the problem is largely mitigated, certain users in specific regions still experience inline signature images loading slowly and the blocking dialog during email send. Because this problem stems from a server-side performance delay, the impact varies by customer and region. Those affected might see delays when loading inline images, particularly in scenarios involving signature add-ins. The product team is actively investigating this problem.

WORKAROUND

Options:

  1. Remove inline images from signature.
  2. Wait for images to load before sending the file.
  3. Switch to classic Outlook for Windows or Outlook for Mac.

EXCEL ISSUE: Increased frequency of RichApi.Error: Error code: 0xF5320001

Since late August, customers report an increase in RichApi.Error 0xF532001 in their error telemetry. This error occurs only when the Office.ribbon.requestUpdate API is called immediately after the Office.ribbon.requestCreateControls API is called.

Tracking ID: 10529994

GitHub issue: Increased frequency of RichApi.Error code 0xF5320001

STATUS

We're currently working on a fix.

START DATE

Reports began late August 2025. Date opened: 09/04/2025

WORKAROUND

Options:

  1. When you make the initial requestCreateControls call, include the enabled or disabled state, if known. Instead of making two calls one right after the other, do it in one call.
  2. Roll back Office from version 2508 to 2507.

RESOLVED: OUTLOOK ISSUE: Add-ins don't load in Outlook LTSC 2024 for new Exchange Online accounts

Some users running the Outlook LTSC 2024 32-bit version can't access Outlook add-ins. Add-ins that previously worked might no longer appear or load.

STATUS

Resolved. To resolve the issue, users must install LTSC 2024 Version 2408 (Build 17932.20976) or later.

Tracking ID: 853980935

START DATE

Date reported: August 19, 2026

RESOLVED DATE

Date fixed: September 8, 2026

DETAILS

Affected client: Outlook LTSC 2024 32-bit version

Customer reports indicate that the issue primarily affects Exchange Online accounts created after June 2026. Older accounts in the same environment and with the same licensing configuration might not be affected.

RESOLVED: ISSUE: PIM-enabled tenants can't deploy or manage Office Add-ins through centralized deployment

When you use Azure AD Privileged Identity Management (PIM) to activate admin roles, a regression error occurs. PIM-enabled admin roles aren't correctly honored. During centralized deployment, role-based access control (RBAC) authorization fails. This failure leads to false permission denials during add-in deployment and management flows.

STATUS

Resolved. The underlying issue is fixed in the April 2026 Monthly Enterprise Channel release (16.0.19822.20180).

IMPACT

Admins can't deploy Office Add-ins through central deployment when using PIM-enabled admin roles.

WORKAROUND

Don't use PIM-enabled roles if this issue blocks you.

RESOLVED: OUTLOOK ISSUE: Classic Outlook on Windows crashes when using signature add-ins

Some users reported that classic Outlook on Windows crashes when using signature add-ins in the following scenarios:

  • Sending mail items through applications other than Outlook. For example, using the Send to > Mail recipient option from a file in File Explorer.
  • Editing an existing calendar item where the user is an organizer.

Affected client version: Classic Outlook on Windows Version 2606 (Build 20131.20090)

STATUS

The fix is included in Version 2606 (Build 20131.20142), Version 2607 (Build 20228.20056), and later. These versions roll out gradually and might not yet be available to all users. Users can update manually once the new version is available, or get the update automatically in a few days.

START DATE

Thursday, July 2, 2026

RESOLVED DATE

Tuesday, July 14, 2026

See Also

Fixes or workaround for recent issues in classic Outlook for Windows Office-js resolved issues in GitHub Deprecation of Exchange Web Services (EWS) in Exchange Online

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