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How to troubleshoot the Exclaimer Outlook Add-in pane not opening in Classic Outlook

  1. Exclaimer Knowledge Base
  2. Solutions
  3. Setup
Ari Flavell
  • Updated

Scenario:

You are using Classic Outlook and the Exclaimer Outlook Add-in is installed. When you select the icon/button for the Add-in in Outlook, the Add-In pane does not open. 

You may also be experiencing the following when this occurs:

  • OWA and New Outlook continue working normally

  • Multiple side-pane/task-pane add-ins are affected

  • Reinstalling or repairing Office has inconsistent results

  • The issue appears after recent Office updates or on specific Outlook builds.

Reason

This behaviour may indicate a broader Classic Outlook Office add-in framework issue rather than an Exclaimer-specific problem.
If multiple add-ins with side-pane interfaces similar to the Exclaimer Outlook Add-in - for example, the Microsoft Outlook add-in My Templates - all fail to open, then the issue is likely related to Classic Outlook itself or the Office Web Add-in runtime.

If these add-in failures occur in Classic Outlook but work in OWA and New Outlook, this may be because of a broader Outlook Office Web Add-in runtime issue rather than an Exclaimer Add-in issue.

Resolution

We recommend you perform the following checks to identify the root of the issue:

  1. Test another add-in with a side-pane interface, such as Microsoft's My Templates. If other add-ins also fail to open, the issue is likely to be with Outlook.
     

  2. Try to open the Add-in in the same mailbox in New Outlook or Outlook on the Web (OWA). If the Add-in will open in a different version of Outlook, the issue is likely to be specific to Classic Outlook. 
     

  3. Update to the latest version of Microsoft 365 Apps/Office if possible. 

Troubleshooting - if you need assistance

For troubleshooting help, see the Troubleshooting section of our interactive guide.

If you need to raise a support ticket, run our diagnostic PowerShell script to help the Support team check your Outlook and Exclaimer Add-In setup. The script safely collects technical details, such as Outlook version, Add-In status, and connectivity, without accessing personal data or emails, enabling faster troubleshooting.
 

 To run the script:

  1. Launch Windows PowerShell. Administrator privileges are optional but recommended.
     

  2. Enter the following command: 

    Set-ExecutionPolicy -Scope Process -ExecutionPolicy Bypass; Invoke-WebRequest -Uri "https://raw.githubusercontent.com/exclaimerltd/Internal-Support-Scripts/master/AddInChecks.ps1" -OutFile "$env:TEMP\AddInChecks.ps1"; & "$env:TEMP\AddInChecks.ps1" 
      
  3. Follow the on-screen prompts.
     

  4. When complete, a report named AddInChecks.html will be generated.

    NOTE: Report Location:
    By default: C:\Users\<YourUser>\Downloads\AddInChecks.html
    Fallback (if Downloads is unavailable): C:\Temp\AddInChecks.html

    Attach the generated file to your Support ticket to allow the Support team to review your configuration. 

If your Support request concerns authentication, include an export of the affected user's Entra ID sign-in logs with your Support ticket. 

To export the logs: 

  1. Sign in to the Microsoft Entra admin centre. 
     
  2. Navigate to Monitoring & health > Sign-in logs.
     
  3. On the Interactive sign-ins tab, filter by the affected user's UPN and the date range covering the issue, then export as CSV.
     
  4. Switch to the Non-interactive sign-ins tab, apply the same filter, and export as CSV. 
     
  5. Attach both CSV files to your support ticket.