The underlying connection was closed: An unexpected error occurred on a receive

[HayS33d]

When I attempt to upload a file to Rackspace I get an error returned from the API
"The underlying connection was closed: An unexpected error occurred on a receive"

The innerException is
The client and server cannot communicate, because they do not possess a common algorithm

Our servers are PCI compliant. I cannot figure what is needed to make this work.

public UploadToCloud(string username, string apiKey)
{
cloudIdentity = new CloudIdentity()
{
Username = username,
APIKey = apiKey
};
}

    public Boolean UploadFile(string fileName, String container)
    {
        FlushError();
        var cloudFilesProvider = new CloudFilesProvider(cloudIdentity);
        if (!File.Exists(fileName))
        {
            errorMessage = fileNotFoundError;
            return false;
        }
        try
        {
            //cloudFilesProvider.CreateContainer("phptest", region:"DFW");
            cloudFilesProvider.CreateObjectFromFile(container, fileName);//, "2017/"+ Path.GetFileName(fileName));
            
            return true;
        }
        catch( Exception e )
        {
            errorMessage = e.Message;
            errorStatus = true;
            return false;
        }
    }

[HayS33d]

Figured it out. Had to force use of .NET 4.6 so TLS 1.2 is used.

[azatabd]

Figured it out. Had to force use of .NET 4.6 so TLS 1.2 is used.

Can you please help with this? Still not clear.