Unable to authenticate Microsoft Dynamics Excel Add In

Question

We have Business Central V19 On premise and we are trying to setup Excel Add in for the first time.

MS Dynamics Excel Add-in Authentication

'https://az689774.vo.msecnd.net' has been blocked by CORS policy: No 'Access-Control-Allow-Origin'

Answer 1

Hi Matt Johnson

Welcome to Microsoft Q&A Forum.

Thanks for sharing the details — the CORS error (No 'Access-Control-Allow-Origin') combined with running Business Central on-premises v19 strongly suggests an authentication request is being blocked due to missing configurations.

Here are some steps that you can kindly follow to help resolve this issue:

1. Enable the Required URLs Through Network/Firewall
   • For the Excel Add-In to load properly-especially to fetch necessary scripts and authentication tokens-it must access various Microsoft-hosted domains. On-prem setups must allow these endpoints in your firewall or proxy:
   • Add-in content and authentication:
   • https://az689774.vo.msecnd.net
   • https://appsforoffice.microsoft.com
   • https://secure.aadcdn.microsoftonline-p.com
   • https://login.microsoftonline.com
   • https://login.windows.net
2. Sign out and reload to clear silent sign-in cache:
   • In the add-in sign-in pane, right-click or tap the blank area to trigger the context menu.
   • Select Reload (or use the Microsoft Dynamics menu if visible) to purge cached sign-in tokens.
   • The login prompt will appear cleanly again, allowing a fresh sign-in.
3. Confirm App Registration and Configuration
   • AAD app must exist for the Excel Add-In, with proper redirect URI (set as SPA) and permissions.
   • In Business Central’s Office App Parameters page:
   • All tabs-App parameters, Registered applets, and Registered resources-should be populated.
   • If any are empty, click Initialize to register the add-in properly.

Please feel free to let me know if you need any further assistance.

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Answer 2

Dear Matt Johnson

Is there any update on this thread?  

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This helps others in the community facing similar problems.  

Thanks for your understanding. 

Answer 3

Hello Matt Johnson

Just checking in to see if the above information was helpful.  

If you have any further updates on this issue, please feel free to post back.  

If you think my reply is helpful to you, please remember to mark it as an answer. Warm thanks.