Event Hub Trigger with Managed Identity not reading events

Question

I have created an Azure Event Hub and an Azure Function with a system-assigned Managed Identity. The Managed Identity has been granted the following roles on the Event Hub: "Azure Event Hubs Data Sender", "Azure Event Hubs Data Receiver", "Azure Event Hubs Data Owner". I have configured the following app settings:

• EVENTHUB_NAME: my_eventhub_name
• EventHubConnection__fullyQualifiedNamespace: my_eventhub_namespace.servicebus.windows.net

Here is the code to write to the Event Hub, which works fine when invoked via HTTP trigger:

import azure.functions as func
import json
import logging
import os

from azure.eventhub import EventHubProducerClient, EventData
from azure.identity import DefaultAzureCredential

app = func.FunctionApp()

# Debugging to check environment variables
logging.info(f"EventHubConnection__fullyQualifiedNamespace: {os.environ.get('EventHubConnection__fullyQualifiedNamespace')}")
logging.info(f"EVENTHUB_NAME: {os.environ.get('EVENTHUB_NAME')}")

EVENTHUBNAMESPACE = os.environ["EventHubConnection__fullyQualifiedNamespace"]
EVENTHUBNAME = os.environ["EVENTHUB_NAME"]

credential = DefaultAzureCredential()

@app.function_name(name="myfunc1")
@app.route(route="myfunc1", auth_level=func.AuthLevel.FUNCTION)
def dora(req: func.HttpRequest) -> func.HttpResponse:
    logging.info('Python HTTP trigger function processed a request.')
    try:
        event_data = req.get_json()
        event_json = json.dumps(event_data)
        producer = EventHubProducerClient(
            fully_qualified_namespace=EVENTHUBNAMESPACE,
            eventhub_name=EVENTHUBNAME,
            credential=credential,
        )
        with producer:
            event_data_batch = producer.create_batch()
            event_data_batch.add(EventData(event_json))
            producer.send_batch(event_data_batch)
        return func.HttpResponse(f"Message '{event_json}' sent successfully to Event Hub.", status_code=200)
    except ValueError:
        return func.HttpResponse("Please pass a valid JSON in the request body with a 'message' key.", status_code=400)
    except Exception as e:
        logging.error(f"Error sending message: {str(e)}")
        return func.HttpResponse(f"Error sending message: {str(e)}", status_code=500)

However, when I deploy the following Event Hub trigger function, it does not read any events unless I replace EventHubConnection__fullyQualifiedNamespace with a connection string in the app settings:

import azure.functions as func
import json
import logging
import os
from azure.eventhub import EventHubProducerClient, EventData
from azure.identity import DefaultAzureCredential

app = func.FunctionApp()

# Debugging to check environment variables
logging.info(f"EventHubConnection__fullyQualifiedNamespace: {os.environ.get('EventHubConnection__fullyQualifiedNamespace')}")
logging.info(f"EVENTHUB_NAME: {os.environ.get('EVENTHUB_NAME')}")

EVENTHUBNAMESPACE = os.environ["EventHubConnection__fullyQualifiedNamespace"]
EVENTHUBNAME = os.environ["EVENTHUB_NAME"]

credential = DefaultAzureCredential()

@app.function_name(name="eventhub")
@app.event_hub_message_trigger(
    arg_name="azeventhub",
    event_hub_name="EVENTHUB_NAME",
    connection="EventHubConnection__fullyQualifiedNamespace",
    consumer_group="function",
    cardinality="one"
) 
def eventhub_trigger(azeventhub: func.EventHubEvent):
    logging.info('Python EventHub trigger processed an event: %s',
                 azeventhub.get_body().decode('utf-8'))

What could be causing the Event Hub trigger function to fail when using Managed Identity, and how can I resolve this?

Thank you.