In applications developed with .net framework, when you use the connection classes under "System.Net (namespace)" and the version you choose for .net framework is below 4.5, you are likely to encounter an error such as "Request stopped: SSL/TLS secure channel could not be established."

If you add the following code to your form's load procedure or before the connection establishment process to resolve the error, your problem will probably be resolved.

ServicePointManager.SecurityProtocol = (SecurityProtocolType)3072;

It was the solution for me.