Error while running the 'Keep alive' schedule task

HI,

I know it is very old thread but today i fixed for me.

Change Execute() function in KeepAliveTask.cs file as below

  public void Execute()
        {
            string url = _storeContext.CurrentStore.Url + "keepalive/index";
            using (var wc = new WebClient())
            {
                wc.Headers.Add("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.2; .NET CLR 1.0.3705;)");
                if(url.ToLower().Contains("https"))
                    ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
                wc.DownloadString(url);
            }
        }

Basically Security Protocol issue.