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Copilot Studio Agent on WhatsApp (ACS) receives messages but does not reply – Event Grid subscription not created

Victor Daniel Tomás Rodríguez 0 Reputation points
2026-01-02T15:03:46.32+00:00

I am integrating a Copilot Studio Agent with the WhatsApp channel using Azure Communication Services (ACS).

Inbound WhatsApp messages are successfully received, but the agent never sends a reply.

Based on investigation, it appears that the Event Grid system topic is created, but no event subscriptions are created, so events are not forwarded to Copilot Studio.

Current State / What Is Working

  • WhatsApp Meta configuration is complete
    • Bring Your Own Number
    • Phone number status: Active
  • Copilot Studio Agent:
    • Published
    • Authentication: No authentication
    • Deployment completed
    • QR code generated successfully
  • Azure subscription:
    • Role: Owner of the subscription
    • Billing configured and active

WhatsApp messages are received by ACS (inbound traffic confirmed)

Azure Configuration Evidence

Event Grid system topic exists and is provisioned successfully:

az eventgrid system-topic list --resource-group <MY_RESOURCE_GROUP>

Output:

  • System topic created
  • ProvisioningState: Succeeded
  • Source: Microsoft.Communication/CommunicationServices
  • Topic type: Microsoft.Communication.CommunicationServices

No Event Grid subscriptions exist (unexpected):

  az eventgrid event-subscription list --source-resource-id "<ACS resource id>"
  • Output:
  []

  az eventgrid system-topic event-subscription list --resource-group <MY_RESOURCE_GROUP> --system-topic-name <MY_SYSTEM_TOPIC_NAME>

Output:

  []

Expected Behavior

When a Copilot Studio Agent is connected to WhatsApp via ACS:

  • An Event Grid event subscription should be automatically created
  • Incoming WhatsApp events should be forwarded to Copilot Studio
  • The agent should respond to messages

Actual Behavior

  • System topic exists
  • No event subscription is created
  • Events are not delivered to Copilot Studio
  • Agent never responds

How can I solve this?

Azure Communication Services

2 answers

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  1. Victor Daniel Tomás Rodríguez 0 Reputation points
    2026-01-05T10:47:05.5766667+00:00

    Thank you very much @Sanket Bhuite

    It was exactly that, already fixed and working.  Thanks have a nice day!

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  2. Sanket Bhuite 0 Reputation points
    2026-01-02T16:44:31.06+00:00

    Root Cause,

    Azure Communication Services (ACS) creates the Event Grid system topic automatically for WhatsApp, but it does not automatically create an Event Grid event subscription. Without an event subscription, incoming WhatsApp events are never forwarded to Copilot Studio, so the agent cannot respond.

    you can do:

    Manually create an Event Grid event subscription that forwards WhatsApp events from the ACS system topic to the Copilot Studio webhook endpoint.

    Steps:

    1. Retrieve the Copilot Studio WhatsApp webhook URL from the agent’s channel configuration.
    2. Create an Event Grid subscription targeting that webhook and include the WhatsApp message event type.
    3. Verify the subscription exists and is in Succeeded state.

    Re-test WhatsApp messaging.

    example:

    az eventgrid system-topic event-subscription create \
  --resource-group <RESOURCE_GROUP> \
  --system-topic-name <SYSTEM_TOPIC_NAME> \
  --name copilotstudio-whatsapp \
  --endpoint <COPILOT_STUDIO_WEBHOOK_URL> \
  --endpoint-type webhook \
  --included-event-types Microsoft.Communication.IncomingMessageReceived

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