Logic App/Power Automate Failure: Persistent 'UnauthorizedGateway' Error on Azure Service Bus Action

Question

We are experiencing a critical failure in our Logic App workflows at the Send message action, which uses the Azure Service Bus connector.

 

The flow consistently fails at this step with the high-level error message: UnauthorizedGateway (or BadGateway).

We have performed extensive troubleshooting and confirmed that the configuration in the failing environment is identical to our working environments (QA/Dev):

 

1.  IAM/Roles: The Managed Identity of the Logic App is correctly configured with the necessary Azure Service Bus Data Sender role.

2.  Connection: The underlying Service Bus API Connection has been validated and/or re-created using the valid Shared Access Policy (SAP) key with Send permissions.

3.  Endpoints: All networking and firewall rules are verified to allow traffic to the Service Bus endpoint. 4.  Parameters: All mandatory parameters, including the Queue/Topic Name, are correctly present in the action definition.

 

Despite confirming that all IAM roles, endpoints, and credentials are in place and correct, the connector continues to return an UnauthorizedGateway error. We require investigation into the connector's behavior and the reason it is failing to authenticate properly.

 

Answer 1

Hi AakVa-1147,

Thanks for reaching out to Microsoft Q&A.

Could you check and confirm below:

1. Go to the API connection in the failing environment: Azure Portal => Resource Group => Connections => <servicebus>
2. Open Edit API connection
3. Select any of the option: Client certificate Auth or Managed Identity

Check if you see "This connection uses Managed Identity" to make sure it is using managed identity.

Recreate the Connection in the Proper Mode to resolve the issue:

1. Delete the existing API connection (servicebus).
2. Recreate a new connection:
   • Authentication: Managed Identity
   • Ensure the Logic App’s System-Assigned or User-Assigned Identity is selected.
3. Assign the following to the identity on the Service Bus namespace:
   • Azure Service Bus Data Sender (or) Azure Service Bus Data Owner
4. Save the connection.
5. Reopen Logic App designer and reselect the connection.

Hope it helps!

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