Error: the remote server returned an error: (401) unauthorized.

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C#

Using the code below I get the following error:

Quote:

"The remote server returned an error: (401) Unauthorized."

This used to work under Windows 7 and VS 2010
Now it doesn't work under Windows 10 VS 2017

NetworkCredential credentials = new NetworkCredential(username, password);

// Create a new WebClient object and set the credentials.
WebClient webClient = new WebClient();
webClient.Credentials = credentials;

String downloadAddress = xxx;

webClient.Headers.Add("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; .NET CLR 1.0.3705;)");

Stream data = webClient.OpenRead(downloadAddress);

I have used both an Anonymous and a specific username and password.

Any help will be greatly appreciated.
Thanks in advance,
Michael

What I have tried:

I have tried multiple things but nothing works.