C# - Could not create SSL/TLS secure channel - Authentication Issues

I am writing code and implementing the code sample in the below url from Silicon Expert.

https://www.siliconexpert.com/apidocs/content/list-part-search

The sample code produced error:  "The request was aborted: Could not create SSL/TLS secure channel."

Searching I found that the below code should be implemented.

ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3 | SecurityProtocolType.Tls | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls12;
ServicePointManager.ServerCertificateValidationCallback += new RemoteCertificateValidationCallback(AllwaysGoodCertificate);

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Below is the full example.  

String username = "MyUserName";
String password = "MyPassword";

ServicePointManager.SecurityProtocol = SecurityProtocolType.Ssl3 | SecurityProtocolType.Tls | SecurityProtocolType.Tls11 | SecurityProtocolType.Tls12;
ServicePointManager.ServerCertificateValidationCallback += new RemoteCertificateValidationCallback(AllwaysGoodCertificate);

string url = "https://app.siliconexpert.com/SearchService/search/authenticateUser?login=" + username + "&apiKey=" + password;
HttpWebRequest request = (HttpWebRequest)WebRequest.Create(url);
request.Credentials = CredentialCache.DefaultCredentials;
CookieContainer cookieContainer = request.CookieContainer = new CookieContainer();
HttpWebResponse response = (HttpWebResponse)request.GetResponse();
String searchUrl = "https://app.siliconexpert.com/SearchService/search/xref?parts=[{\"partNumber\":\"bav99\"}]&crossType=B";
request = (HttpWebRequest)WebRequest.Create(searchUrl);
request.CookieContainer = cookieContainer;
response = (HttpWebResponse)request.GetResponse();
String results = new System.IO.StreamReader(response.GetResponseStream(), ASCIIEncoding.ASCII).ReadToEnd();
Console.WriteLine(results);
Console.ReadLine();

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I am receiving

<?xml version="1.0" encoding="UTF-8"?><ServiceResult><Status><Code>1</Code><Message>Invalid User Name Or Password</Message><Success>false</Success></Status></ServiceResult>

Yet, when I log into the site and perform a search there is no issue.

Anyone see anything that I'm missing?  Want to check to see if it is the code or the site.