Based on what you've already checked, I would focus less on Azure RBAC at this point and more on whether the Copilot Studio environment is eligible to provision/discover the WhatsApp channel.
A few observations:
1. The Teams/Microsoft 365 channel working does not validate WhatsApp provisioning
Those channels use a different provisioning path. So the fact that the agent works in Teams confirms that the agent itself is healthy, but it doesn't necessarily prove that the environment can enumerate WhatsApp accounts through Azure Communication Services.
The key failure appears to be here:
.../api/channels/whatsapp
returning 404.
If the Copilot Studio backend endpoint responsible for the WhatsApp channel is returning 404, that would explain why the UI falls back to:
There are no WhatsApp accounts associated with the selected Azure Communication Services resource.
In other words, the message may be misleading: the issue may not actually be that ACS cannot see the WhatsApp Business Account.
2. I would specifically test this in a non-Developer environment
This is the first thing I would try.
Create or use a sandbox/production environment in the same region, create a minimal test agent, and attempt to connect the exact same ACS resource.
If:
Developer environment → WhatsApp channel API returns 404
Sandbox/Production → WhatsApp account is discovered
then you have a strong reproducible case that the issue is related to environment type or backend rollout/provisioning, rather than the ACS configuration.
I would not spend more time repeatedly changing Contributor/Owner assignments if the ACS resource is already visible to Copilot Studio and the WhatsApp account is correctly configured in Azure.
3. Check that the ACS resource meets the Power Platform integration requirements
In addition to RBAC, verify the exact prerequisites required for the Copilot Studio ↔ Azure Communication Services WhatsApp integration, including:
- Same Microsoft Entra tenant
- Supported ACS/WhatsApp configuration
- Correct Azure subscription visibility
- Required enterprise application permissions
- Required Azure resource provider registration
- Supported Power Platform region/environment configuration
The official setup documentation is the best checklist for this because the required service principals and permissions can change. I would compare the configuration line by line rather than relying only on the fact that the WhatsApp sender is visible in the Azure portal.
4. The island hostname is probably not something you can or should change
The gateway hostname is part of Microsoft's managed Power Platform infrastructure. There is no supported mechanism to manually select the Copilot Studio backend cluster or move an existing agent from an island gateway to another cluster.
Therefore, I would treat:
powervamg.eu-il109.gateway.prod.island.powerapps.com
as a useful diagnostic detail for Microsoft Support, but not as something that can be manually reconfigured by the customer.
5. The 404 is worth escalating
Since:
- the ACS resource is discoverable in the UI,
- the WhatsApp Business Account and sender are visible in ACS,
- the required tenant relationship has been verified,
- RBAC has been tested at wider scopes,
- the issue persists beyond normal permission propagation,
- and the Copilot Studio WhatsApp backend request itself returns 404,
I think this has moved beyond normal configuration troubleshooting.
My recommended next step would be to open a Microsoft support request and include:
- Environment ID
- Environment type and region
- ACS resource ID
- Approximate timestamps in UTC
- The exact WhatsApp Business Account/Sender configuration
- The failing
/api/channels/whatsapp request and 404 response
- A HAR file if Support requests it
- Confirmation that the same ACS resource was tested against another supported Power Platform environment, if possible
I would also include the comparison result if you test the same ACS resource from a Sandbox environment. That would be particularly valuable because it would help separate an ACS discovery problem from a Developer-environment/backend provisioning limitation or service regression.
So, based on the evidence provided, I would not assume that the WhatsApp Business Account is missing or incorrectly linked. The 404 from the Copilot Studio WhatsApp channel backend suggests the channel discovery/provisioning path itself may not be available for that environment.
At this point, testing the same ACS resource against a supported Sandbox/Production environment and then raising a Microsoft support case with the 404 evidence would be the most useful next step.
