How to resolve unknown differences between new HttpClient instance and HttpClientFactory instance

Currenty I'm building a solution which is basically an integration between multiple external REST services. Since the solution is having multiple external service, I want to use the .NET ClientFactory to create HttpClients whenever they are wanted. Unfortunately an HttpClient instance created from the ClientFactory always results in an Unauthorized. This is a bit strange since directly creating a new HttpClient results in a success. I red the Microsoft documentation about the HttpClientFactory to determine the differences and possible use cases.

I compared the two different HttpClient instances by extracting the entire objects and did a meld comparison without any differences. Also with postman the call to the service succeeds.

The code which extracts and creates the HttpClient instance (which fails) looks like this:

Program.cs

 ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12; services.AddHttpClient("ClientName", client => {     client.BaseAddress = new Uri("https://my.domain.com");     var credentials = Convert.ToBase64String(Encoding.UTF8.GetBytes("username:password"));     client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Basic", credentials);     client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json")); });

TicketRepository.cs

public class TicketsRepository(    IHttpClientFactory _httpClientFactory) : ITicketsRepository{    private readonly HttpClient _httpClient = _httpClientFactory.CreateClient("ClientName");    public async Task<Tickets> GetTicketByNumber(        int ticket,        CancellationToken cancellationToken)    {        HttpResponseMessage response = await _httpClient.GetAsync(            $"{Constants.TicketsUrlTemplate}/{ticket}",            cancellationToken);        if (!response.IsSuccessStatusCode)        {            _logger.LogError("Could not successfully retrieve data. Invalid response data is: {response}", response.ToString());            throw new HttpRequestException($"Server did not respond with an http response status 200: {response}");        }        return new Tickets();    }}

The code which creates an HttpClient instance on every method call and succeeds extracting data looks like this:

public async Task GetTicketByNumber(    int ticket,    CancellationToken cancellationToken){    using (HttpClient client = new HttpClient())    {        client.BaseAddress = new Uri("https://my.domain.com");        var credentials = Convert.ToBase64String(Encoding.UTF8.GetBytes("username:password"));        client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Basic", credentials);        client.DefaultRequestHeaders.Accept.Add(new MediaTypeWithQualityHeaderValue("application/json"));        try        {            HttpResponseMessage response = await client.GetAsync($"/urlTemplate/{ticket}/", cancellationToken);            string responseContent = await response.Content.ReadAsStringAsync();            Console.WriteLine("Response Content: " + responseContent);        }        catch (HttpRequestException e)        {            Console.WriteLine("Request error: " + e.Message);        }    }}

I did a blank comparison with the Response Objects and HttpClient Objects with identical headers, version, host etc... I must have overlooked something stupid since the ClientFactory works for other Rest Services configured on startup. It is hard to monitor stuf on the server side, since I do not have any physical acccess towards that REST Service, nor do I have access to the source of it. Hopefully someone can point me in the right direction.