Storage queue trigger not firing in .NET isolated Azure Functions app, works locally

I’m deploying a new .NET isolated Azure Functions app and I’m stuck on a problem where my storage queue triggers never fire in Azure, even though the same project works locally in VS Code.

I’d appreciate help understanding what I might be missing.

Environment

Azure Functions runtime: v4

Worker model: .NET isolated

Target framework: .NET 9 (net9.0)

OS: Linux

Hosting plan: Flex Consumption (Linux)

Key packages:

• Microsoft.Azure.Functions.Worker 2.51.0
• Microsoft.Azure.Functions.Worker.Sdk 2.0.7
• Microsoft.Azure.Functions.Worker.Extensions.Storage 6.8.0
• Microsoft.Azure.Functions.Worker.Extensions.DurableTask 1.11.0

Storage:

• One storage account (call it xxxxxxxxxxxxxx) that holds business queues, e.g. xxxxxx-queue, [email-messages], etc.
• A separate storage account is used for AzureWebJobsStorage / Durable state.
• The xxxxxxxxxxxx storage account is in a different subscription/resource group than the Function App, but in the same AAD tenant.

Code (queue trigger)

A simplified version of my queue-triggered function:

public static class functionName

{

    [Function("FunctionName")]

    public static async Task RunAsync(

        [QueueTrigger("<queueName>", Connection = "QueueStorageAccount")]

        string orderMessage,

        FunctionContext context)

    {

        var log = context.GetLogger<OrderProcessorFunction>();

        log.LogInformation("Processing order: {OrderMessage}", orderMessage);

        // ... business logic ...

    }

}

There are similar triggers for other queues (e.g. email-messages), all using Connection = "QueueStorageAccount".

Configuration (Azure App Settings)

For QueueStorageAccount I’ve tried two approaches.

Using a connection string

• QueueStorageAccount = connection string for the storage account (standard storage account; connection string verified: I can list/add messages via Storage Explorer).
• QueueStorageAccount__accountName and QueueStorageAccount__credential are not set. In the Function’s Integration blade for OrderProcessorFunction:
• Binding type: Azure Queue Storage
• Storage account connection: QueueStorageAccount (shows as configured, no warning)
• Queue name: xxxxxxxxx

**
Using managed identity (earlier attempt)**

• QueueStorageAccount__accountName = xxxxxxxxxxxxx
• QueueStorageAccount__credential = managedidentity
• QueueStorageAccount (no suffix) not set.
• The Function App’s system-assigned managed identity has the [Storage Queue Data Contributor] role on the xxxxxxxxxxxstorage account. In both setups:The target queue xxxxxxxxxxxx exists in xxxxxxxxxxxxxx.
• Manually enqueued messages show up in the queue.
• DequeueCount stays at 0 for all messages.

What works

• The project runs fine locally in VS Code (.NET isolated worker, func start), targeting:
  • Azurite, or
  • A real Azure Storage account via connection string.
• An HTTP-triggered function in the same app runs in Azure and successfully enqueues messages into xxxxxxxxxxxxxxx using a helper like:

public static async Task<Response<SendReceipt>> EnqueueOrderAsync(string message)
{
    return await _ordersQueueClient.SendMessageAsync(message);
}

After calling the HTTP function, I can see new messages in xxxxxxxxxxxxxx in the xxxxxxxxxxxxxxxxxxxx storage account.

So enqueueing from this Function App to the queue works in Azure.

What doesn’t work

• In Azure, the xxxxxxxxxxxxxxxxxxxxxxxx:
  • Is listed in the Functions blade.
  • Status is Enabled.
  • Shows no invocations in the Monitor tab (past 30 days).
  • Messages remain in xxxxxxxxxxxxxxxxxx indefinitely; DequeueCount is 0, even after:
  • Restarting the Function App.
  • Redeploying the app (fresh publish).
  • Manually adding test messages like "hello world" to the queue.

There is no corresponding poison queue (e.g. xxxxxxxxxxxxxxxx-poison), which suggests the trigger never runs at all.

Diagnostics and logs

• Application Insights traces show:
  • At startup: a list of discovered functions, including something like Host.Functions.OrderProcessorFunction.
  • Occasionally: Stopped the listener 'Microsoft.Azure.WebJobs.Script.Description.FunctionGroupListenerDecorator+NoOpListener' for function 'xxxxxxxxxxxxxxxxxx'.
• I do not see:
  • “Error indexing method 'OrderProcessorFunction' …”
  • “The listener for function 'OrderProcessorFunction' was unable to start …”
  • “Storage account connection string 'QueueStorageAccount' is missing or invalid …”
  • Any exceptions where operation_Name is xxxxxxxxxxxxxxxxxxxxxxxxxx.

When I enqueue “bogus” messages like "hello world" to xxxxxxxxxxxxxx, I would expect at least a deserialization error and an invocation, but there are no invocations recorded at all.

Question

Given:

• The code and triggers work locally.
• The app in Azure can write to the queue (using the same connection name/config), but never reads from it.
• The function is enabled, there are visible messages, but no invocations and no obvious indexing errors.

Is there anything specific to:

• .NET isolated + Microsoft.Azure.Functions.Worker.Extensions.Storage 6.8.0,
• My hosting plan (Flex Consumption, Linux), or
• Using a storage account in a different subscription,

that would cause the queue trigger to end up with a NoOpListener and never actually poll/process messages, even though the binding appears valid in the Integration blade?

What additional diagnostics or configuration would you recommend to help me understand why this queue-triggered function is never being invoked in Azure?