I'm trying to fetch MongoDB Atlas logs via a function app, but unable to get correct nonce value.

Question

I've encountered a problem that I haven't been able to solve for a while now.

Purpose
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An azure function that downloads audit logs from MongoDB Atlas and stores it in an azure storage container.

Setup
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Mongo DB Atlas cluster and function are only accessible when connected to a VPN. MongoDB requires additional auth otherwise returns access denied. I'm using digest authentication. I've tested downloading the file via postman, and sending it to be stored in a storage container. Both work as expected.

Issue
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1. My code makes a request which is rejected.
2. The headers are parsed to extract the realm and nonce.
3. Values are taken in by a helper method that generates a digest header.
4. Digest header is added to DefaultRequestHeaders.
5. 2nd request is made but auth fails. Nonce returned is different to nonce supplied (presumably because each request generates a unique value).

Question
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What am I doing incorrectly? My guess is that making the second request is somehow wrong and I need to return header during the 1st request - otherwise I don't understand how I get the nonce value from an api request before calling it (which is impossible afaik)

Code
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using System.Collections.Generic;
using System;
using System.Net.Http.Headers;
using System.Security.Cryptography;
using System.Text;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Http;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Azure.Functions.Worker;
namespace mongoDB_Atlas.logs.ExternalApiFunction
{
    public class Class1
    {
        // Client.
        private static readonly HttpClient client = new HttpClient();
        //--------------------------------------------------------------------------------------//
        // No Auth Function
        //--------------------------------------------------------------------------------------//
        [Function("no-auth")]
        public static async Task