C# HttpClient Not Working on 1 Site - TLS Error

Question

I am running into an odd TLS error when using HttpClient in a .NET 6 app. The code is pretty simple and works 99.9% of the time. However, there is one site (ultipro.com) that keeps failing on TLS Handshake. I've looked at their site/certificates and they use TLS1.2 which should be no problem for this version of .NET.

My code:

try
{
    string url;  

    //Examples: These do not work --> SSL Error
    url = "https://recruiting.ultipro.com/LOS1000LADOD/JobBoard/5365ad6e-23ff-4703-bb77-1e9451fb855e/OpportunityDetail?opportunityId=3b914758-c414-4f1d-a8f2-7d5c0e453cca";
    //url = "https://recruiting.ultipro.com/GRA1017GRYT/JobBoard/ae441110-89bd-444d-8ad2-b76c7b9db7a9/OpportunityDetail?opportunityId=acb56de2-b21f-49a1-9c48-7da6d7e47491"

    //Example: Works fine
    //url = "https://www.foxcareers.com/Search/JobDetail/R50016539"; 

    using (var client = new HttpClient())
    {
        var httpRequestMessage = new HttpRequestMessage(HttpMethod.Get, url);

        var response = await client.SendAsync(httpRequestMessage);

        if (response.IsSuccessStatusCode)
        {
            using (var contentStream = await response.Content.ReadAsStreamAsync())
            {
                StreamReader reader = new StreamReader(contentStream, Encoding.GetEncoding("utf-8"));
                string content = reader.ReadToEnd();
            }
        }
        else
        {
            Console.WriteLine("Internal server Error");
        }
    }


}
catch (Exception ex)
{
    string errormsg = ex.Message;
}

The Error:

The SSL connection could not be established, see inner exception.

Inner Exception: Authentication failed because the remote party sent a TLS alert: 'HandshakeFailure'.
Source: System.Net.Security

I've tried everything I can think of including adding/removing different headers and specifying the TLS version. Ex:

ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;

These URLs work just fine in my browser and Postman. Any ideas on what I'm overlooking?

Answer 1

UPDATE 1-6-2022:

OK - This is weird but everything seemingly got fixed overnight on their end. Code works just fine now. Maybe they introduced a bad cipher and I just happened to run into it exactly on the day they were fixing it but I have no problems this morning. Seems like a big coincidence but at least good folks like @Julian helped me know that I'm not crazy.