Outlook Add-in Missing After License Change (Fix)

Short answer

If the add-in is missing in Classic Outlook after switching licenses, the cause is typically related to deployment, policies, or Outlook cache — not the license itself.

1. Confirm the add-in is deployed

• Go to Microsoft 365 Admin Center
• Navigate to: Settings > Integrated apps
• Verify:
  • The add-in is still deployed
  • It is assigned to the correct users or groups

If the add-in is missing or not assigned correctly, redeploy it.

2. Check if the add-in works in Outlook on the web (OWA)

• Open Outlook on the web
• Create a new email
• Check whether the add-in appears

Result:

• Works in OWA → The issue is specific to Classic Outlook (client-side)
• Does not work in OWA → The issue is related to deployment or policy

3. Verify add-ins are allowed (Mailbox policy)

Check that Office add-ins are enabled in Exchange Online.

Run the following in Exchange Online PowerShell:

Get-OwaMailboxPolicy | Select Name, AppsForOfficeEnabled

Ensure AppsForOfficeEnabled = True.

If disabled, enable it for the affected users.

4. Check Outlook (Classic) add-in status

In Outlook:

• Go to: File > Options > Add-ins
• Review:
  • Manage: COM Add-ins > Go
  • Manage: Disabled Items

Even though this is not a COM add-in, Outlook may disable related components that affect add-in loading.

5. Restart Outlook and clear local cache

• Fully close Outlook (including background processes)
• Reopen Outlook

If the issue persists:

• Create a new Outlook profile
• Or sign out of Office and sign in again

6. Verify WebView2 is installed and updated

Classic Outlook depends on Microsoft Edge WebView2 Runtime for modern add-ins.

• Confirm WebView2 is installed
• Update to the latest version if needed

7. Check network and security restrictions

Ensure the environment allows access to required services:

• Microsoft 365 endpoints
• Add-in service endpoints

Review:

• Firewall rules
• Proxy configuration
• Endpoint security tools (e.g. Microsoft Defender, Acronis)

8. Review Intune / App Protection policies

If Microsoft Intune is used, verify that policies do not block:

• Office add-ins
• Embedded web content in Office apps
• Authentication, cookies, or session handling

9. Reassign the license and refresh sign-in

• Remove the Business Premium license
• Assign it again
• Ask the user to:
  • Sign out of Office
  • Sign in again

This step helps refresh service tokens and permissions.

10. Test on another device

• Sign in with the same user account on another machine

Result:

• Works on another device → Device-specific issue
• Does not work → User, policy, or deployment issue

Summary

After switching from E3 to Business Premium, missing add-ins in Classic Outlook are usually caused by:

• Missing or incorrect add-in deployment
• Mailbox or security policies blocking add-ins
• Outlook profile or cache issues
• WebView2 runtime missing or outdated
• Network or endpoint restrictions