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ACS webhook authentication to Contact Centre

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Posted on by SA-30061402-0

Currently having significant issues with setting up an Azure Communication Services Event to send an incoming call into Dynamics.

Followed all the documentation, keep getting the following error:

Categories:

Dynamics 365 Contact Center

Dynamics 365 Customer Service

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SA-30061402-0 11 on at

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ACS webhook authentication to Contact Centre

Thank you both for your responses, just wanted to provide some additional detail.

I have followed the steps in this article here: Secure WebHook delivery with Microsoft Entra ID - Azure Event Grid | Microsoft Learn

The apps are in the same tenant

event subscription is being configured by application

I have updated these variables to match

$webhookAppObjectId: Microsoft Entra application ID created for the webhook (Dynamics 365 Customer Service/Contact Centre)

$eventSubscriptionWriterUserPrincipalName: Azure user principal name of the user who creates event subscription (Azure Communications Services Service Principal)

AzureEventGridSecureWebhookSubscriber has been created and assigned to the Event Subscription Writer

I have the Application Administrator role in Entra

Event Grid subscription writer app has the Event Grid Contributor role

I am using the Azure Shell, Powershell environment

I have signed in to the Azure shell using the Event Grid subscription writer Microsoft Entra Application

I am getting the same error when running this script in Azure Shell:

(URL validation) Webhook validation handshake failed for https://v-c3f5a89b-f956-f011-8ee6-002248c6b6a6.uk.omnichannelengagementhub.com/dynamics/omnichannel/voice/incoming. Http POST request failed with response code Unknown. For troubleshooting, visit https://aka.ms/esvalidation. Activity id:dd2582b8-3e18-4450-a184-9979c2b34b49, timestamp: 8/20/2025 2:05:59 PM (UTC).
Code: URL validation
Message: Webhook validation handshake failed for https://v-c3f5a89b-f956-f011-8ee6-002248c6b6a6.uk.omnichannelengagementhub.com/dynamics/omnichannel/voice/incoming. Http POST request failed with response code Unknown. For troubleshooting, visit https://aka.ms/esvalidation. Activity id:dd2582b8-3e18-4450-a184-9979c2b34b49, timestamp: 8/20/2025 2:05:59 PM (UTC).

Re your comments:

Public Access: Make sure your webhook URL is publicly reachable and not blocked by firewalls or IP restrictions

This has been set to public network

Validation Response: Your endpoint must respond to the Event Grid validation event with the correct validation code. This is required for handshake completion.

This could be one of the issues I'm having. How do i confirm this is setup correctly?

HTTPS/TLS: Ensure your endpoint uses HTTPS with a valid, trusted SSL certificate.

This could also be one of the issues I'm having. How do i confirm this is setup correctly?

Managed Endpoint Checks: If the endpoint is hosted in Dynamics or Omnichannel, confirm it’s configured to accept Event Grid validation requests.

Again on this point, how do I confirm this is configured correctly?

Thank you both for your help with this, it is appreciated

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Nour Abuzaid 121 on at

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ACS webhook authentication to Contact Centre

Here’s a concise explanation for your ACS webhook authentication issue with Dynamics 365 Contact Center:

The “Webhook validation handshake failed” error occurs because Azure Event Grid couldn’t successfully validate your endpoint. To fix it:

Public Access: Make sure your webhook URL is publicly reachable and not blocked by firewalls or IP restrictions.

Validation Response: Your endpoint must respond to the Event Grid validation event with the correct validation code. This is required for handshake completion.

HTTPS/TLS: Ensure your endpoint uses HTTPS with a valid, trusted SSL certificate.

Managed Endpoint Checks: If the endpoint is hosted in Dynamics or Omnichannel, confirm it’s configured to accept Event Grid validation requests.

Reference: https://learn.microsoft.com/en-us/azure/event-grid/security-authentication
.

In short: the endpoint must be publicly accessible, respond correctly to validation events, and support secure HTTPS.

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DAnny3211 10,782 Moderator on at

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ACS webhook authentication to Contact Centre

Hi,

Thank you for sharing the error details. The issue you're encountering during the webhook validation handshake typically points to a problem with the endpoint not responding as expected during the Azure Event Grid subscription setup.

Here are a few things to check:

Ensure the endpoint is publicly accessible and not behind a firewall or authentication layer that blocks Azure’s validation request.

Verify that the endpoint supports the validation handshake required by Azure Event Grid. This involves responding to the validation event with the correct validation code.

Check TLS/SSL configuration on the endpoint. Azure requires secure HTTPS communication with a valid certificate.

Review the documentation at aka.ms/esvalidation for detailed troubleshooting steps and examples of how the endpoint should respond.

If the endpoint is hosted within Dynamics or a managed service, you may need to confirm with your environment administrator that it’s configured to accept and respond to Azure Event Grid validation requests.

Please verify if this response was helpful.

Thanks and best regards,
Daniele
Note: This response was prepared with support from Copilot to ensure clarity and completeness.

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