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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DAnny3211 11,417 Super User 2026 Season 1 on at

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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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Nour Abuzaid 197 on at

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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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SA-30061402-0 37 on at

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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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SA-30061402-0 37 on at

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Just wanted to provide an update on this

Managed to get it working correctly!

I deleted all of the created resources in Azure, aside from the Subscription and the resource group

I created a new Azure resource following the steps here:Connect using a new Azure resource | Microsoft Learn

Fulfilling the following prerequisites:

Check whether the Get started button to connect to an existing Azure resource is visible on the Phone numbers page. The Get Started button appears only in the following scenarios.

The trial ends after the free calling time elapses.

You manually ended the trial.

Trial was previously manually ended

You disconnected from the Azure resource. For more information, refer to Disconnect from Azure Communication Services resource.

I think we may have connected to the previous ACS resource so this was deleted and recreated

Have an Azure subscription that's in the same tenant as your Dynamics 365 account. Ensure that your Azure subscription meets the Subscription eligibility and number capabilities requirements.

correct tenant (same tenant) confirmed

Have at least contributor-level permissions to the Azure subscription. To check your role, open your subscription and view the My role column of your subscription on the Azure portal. You can deploy your Azure Communication Services resource only if you have contributor-level permissions.

confirmed to have correct permissions as owner of resource/global admin

I think this was one of the key steps that may have been misconfigured previously:

You might be prompted to add an Event Grid app ID for your resource. If you see this option, refer to Get Event Grid application and tenant IDS from the Azure portal for information about these values.

I created a new Azure resource in the Contact Centre admin centre, as here:

Once this was registered here, it was added to app registrations in Azure, including for the Incoming call, call recording and SMS webhooks

This showed that Azure was correctly pulling through the webhook information from Dynamics

My advice for anyone having a similar issue in future is to remove and recreate all Azure resources aside from the Azure subscription and the resource group, and to follow this

Connect using a new Azure resource | Microsoft Learn

and this

Set up incoming calls, call recording, and SMS services | Microsoft Learn

and it should resolve the issue. If setup correctly the event subscriptions should pull through from Dynamics as above and be listed under Event Grid System Topic -> Subscriptions within the Azure resource on the Azure Portal

Azure setup within Contact Centre admin centre in Dynamics should look like the following:

The event grid app id should match the Azure app registration for the Azure communication resource here, highlighted in yellow:

This should correctly configure the Event Grid to deliver events to the Dynamics webhooks in order to deliver calls and SMS to Dynamics in order for users in the Contact Centre workspace to receive incoming calls. You will then need to configure both Voice channels and workstreams in order to manage the incoming calls, assign them to users/routing, and configure default behaviour of the D365 interface

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