Httpclient could not create ssl/tls secure channel

Simply add following line before httpclient initialization code: ServicePointManager.SecurityProtocol = (SecurityProtocolType)768 | (SecurityProtocolType)3072; Complete code will look something like this: ServicePointManager.SecurityProtocol = (SecurityProtocolType)768 | (SecurityProtocolType)3072; using (var httpClient = new HttpClient()) { httpClient.BaseAddress = new Uri(Constant.Endpoint.Event.Base); var access_token = GetAccessToken(); httpClient.DefaultRequestHeaders.TryAddWit...

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