Power Platform Community Forum Thread Details

Hi everyone,

I am trying to publish a Copilot Studio agent to WhatsApp using Azure Communication Services (ACS), but the channel deployment is failing during the Event Grid webhook validation step.

Scenario

We are using:

Copilot Studio agent
Azure Communication Services
ACS Advanced Messaging / WhatsApp channel
WhatsApp Business number connected through Meta
Azure Event Grid

The WhatsApp number is already connected and active in both Meta Business and ACS.

In Copilot Studio, the agent is:

Published
Configured with No authentication
Working correctly in the internal Copilot Studio test pane

What happens

When I go to:

Copilot Studio → Agent → Channels → WhatsApp

and select:

Azure subscription
ACS resource
WhatsApp phone number

then click Deploy, the wizard shows the connection/loading message and then returns to the initial WhatsApp setup screen.

In some attempts, the channel appeared as connected and generated the QR code, but inbound WhatsApp messages did not trigger any response from the agent.

Initial issue

At first, the HAR showed:

HTTP 403 Forbidden

with a message indicating insufficient permissions to provision/operate Microsoft.EventGrid.

We granted temporary Contributor permissions at the Azure subscription scope, and the 403 error was resolved.

Current issue

After fixing the permission issue, the deployment now fails with:

HTTP 500 Internal Server Error

on the operation:

POST /chatbotmanagement/.../api/channels/whatsapp/add

The response indicates:

Webhook endpoint validation failed

for an Event Grid subscription similar to:

/subscriptions/<subscription-id>/resourceGroups/<resource-group>/providers/Microsoft.EventGrid/systemTopics/<acs-system-topic>/eventSubscriptions/whatsapp-appId-...

with:

Status: Failed
Status code: 400 Bad Request
ErrorCode: InvalidRequest

What we already validated

To isolate the issue, I manually created an Event Grid subscription on the ACS system topic for:

Microsoft.Communication.AdvancedMessageReceived

and pointed it to an Azure Event Grid Viewer endpoint.

When I sent a WhatsApp message to the ACS-connected number, the event was successfully received in Event Grid Viewer.

The event payload confirmed:

eventType: Microsoft.Communication.AdvancedMessageReceived
channelType: whatsapp
content: "ola"
from: <my WhatsApp number>

Event Grid metrics also showed:

Published Events: 1
Matched Events: 1
Delivered Events: 1
Delivery Failed Events: 0

So the following flow appears to be working:

WhatsApp / Meta → ACS → Event Grid

The remaining issue seems to be:

Event Grid → Copilot Studio managed webhook endpoint

Question

For the native Copilot Studio WhatsApp channel, should Copilot Studio automatically create and validate its own Event Grid subscription/webhook endpoint?

Has anyone seen this error before?

Webhook endpoint validation failed
HTTP 500 Internal Server Error
400 Bad Request / InvalidRequest
during Copilot Studio WhatsApp channel deployment via ACS.

Any guidance on hidden prerequisites, tenant policies, regional limitations, required roles, or known issues with the managed Copilot Studio webhook would be appreciated.

Thanks.

Categories:

Publish & channel management