Why is my Azure Function stuck in read-only mode?

I am attempting to deploy a small piece of python code to the Azure cloud. I want a function which makes a request to an API, manipulates the response, and puts the output into a CSV file all in Azure. It stores and retrieves the API keys from the Azure Keyvault.

I am unable to run my code as the Function is stuck in read-only mode, so it cannot create a new CSV file as is needed.

Here's what I've done so far:

1. Created a new resource group for the resources.
2. Created a new function app running on Linux. It is set to python runtime.
3. Created dedicated App Service Plan and Application Insights resources for the function app.
4. Created a KeyVault and stored the API keys as a KV Secret.
5. Created a system assigned managed identity for the Azure Function, and created a new set of Keyvault policies to allow the Function access to 'get' KV secrets.
6. Linked the Keyvault and Function by adding the Keyvault identity(?) to the Function's application settings.
7. In the Function's application settings, set FUNCTION_APP_EDIT_MODE to 'readwrite'. Also set WEBSITE_RUN_FROM_PACKAGE to '0' (also tried this as '1' but to no avail).

For context, I am deploying the function itself using the Azure Functions extension in VS Code.

Any suggestions about how to allow the writing of a new CSV file would be appreciated. Alternatively, any suggestions for alternatives method to run this code in Azure would also be welcomed.

Edit: Could the problem here actually be that the code is not outputting to the attached storage account? That the function is read-only might not be the true problem here...

My function.json file:

{
  "scriptFile": "__init__.py",
  "bindings": [
    {
      "name": "mytimer",
      "type": "timerTrigger",
      "direction": "in",
      "schedule": "0 0 4 * * *"
    },
    {
      "name": "outputFile",
      "direction": "out",
      "type": "file",
      "path": "output/csv",
      "connection": "AzureWebJobsStorage"
    }
  ]
}

A snippet of my __init__.py file which attempts to write to a CSV file and place in storage:

with open("non_exempt_devices.csv", "w", newline="") as f:
      writer = csv.writer(f)
      writer.writerow(["Host Name", "Metadata"])
      writer.writerows(output[0])
      outputFile.set(f)

>Why is my Azure Function stuck in read-only mode?

1. When you deploy the function app (dll files) for the 1st time, it will be in read-only mode.
2. Even you delete or disable the application setting WEBSITE_RUN_FROM_PACKAGE, until you publish the function app with some changes next time then read-only mode will not disappear.
3. You can also publish the Azure Functions project without zip to rid out of the read-only mode.
   I know that you’re using the VS Code where we have the Publish the Azure Functions Project without zip in Visual Studio but not in VS Code.

Then you can make use of the command to deploy/upload without zip to the function app as given in this SO Answer.