Please add the following before using HttpClient to request from https://app.vssps.visualstudio.com/oauth2/* ` System.Net.ServicePointManager.SecurityProtocol = System.Net.SecurityProtocolType.Tls12; ` I've placed in **Global.asax.cs** which worked for me.
Please add the following before using HttpClient to request from https://app.vssps.visualstudio.com/oauth2/*
System.Net.ServicePointManager.SecurityProtocol = System.Net.SecurityProtocolType.Tls12;I've placed in Global.asax.cs which worked for me.