Azure Multi-Factor Authentication onprem Server User Portal

[SocketException (0x2746): An existing connection was forcibly closed by the remote host]
   System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size) +249

[IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host.]
   System.Net.Sockets.NetworkStream.Read(Byte[] buffer, Int32 offset, Int32 size) +8422189
   System.Net.FixedSizeReader.ReadPacket(Byte[] buffer, Int32 offset, Int32 count) +57
   System.Net.Security.SslState.StartReceiveBlob(Byte[] buffer, AsyncProtocolRequest asyncRequest) +243
   System.Net.Security.SslState.StartSendBlob(Byte[] incoming, Int32 count, AsyncProtocolRequest asyncRequest) +470
   System.Net.Security.SslState.ForceAuthentication(Boolean receiveFirst, Byte[] buffer, AsyncProtocolRequest asyncRequest) +8553310
   System.Net.Security.SslState.ProcessAuthentication(LazyAsyncResult lazyResult) +230
   System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx) +645
   System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx) +9
   System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state) +87
   System.Net.TlsStream.ProcessAuthentication(LazyAsyncResult result) +1467
   System.Net.TlsStream.Write(Byte[] buffer, Int32 offset, Int32 size) +84
   System.Net.ConnectStream.WriteHeaders(Boolean async) +816

[WebException: The underlying connection was closed: An unexpected error occurred on a send.]
   System.Web.Services.Protocols.WebClientProtocol.GetWebResponse(WebRequest request) +801829
   System.Web.Services.Protocols.HttpWebClientProtocol.GetWebResponse(WebRequest request) +10
   System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String methodName, Object[] parameters) +270
   pfup.pfwssdk.PfWsSdk.TestSecurity() +50
   pfup.login.Page_Load(Object sender, EventArgs e) +923
   System.Web.UI.Control.LoadRecursive() +71
   System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint) +3178