Call cannot get connected

UCMA app receives an incoming call, but it cannot get connected.

the following is the states of that call:

Underlying call state changed from Incoming to Establishing

Underlying call state changed from Establishing to Terminating

Underlying call state changed from Terminating to Terminated

The following is the exception encountered:

Request is already terminated  FailureReason = 0 Microsoft.Rtc.Collaboration.CallOperationFailureException:Request is already terminated ---> Microsoft.Rtc.Collaboration.OfferAnswerException:Request is already terminated

   at Microsoft.Rtc.Signaling.SipAsyncResult`1.ThrowIfFailed()

   at Microsoft.Rtc.Collaboration.ComponentModel.MediaProvider.EndGetAnswerInternal(IAsyncResult result)

   at Microsoft.Rtc.Collaboration.Call.EstablishCoreAsyncResult.OfferAnswerRequestCompleted(IAsyncResult result) Detected at System.Environment.GetStackTrace(Exception e, Boolean needFileInfo)

   at System.Environment.get_StackTrace()

   at Microsoft.Rtc.Signaling.RealTimeException..ctor(String message, Exception innerException)

   at Microsoft.Rtc.Collaboration.OfferAnswerException..ctor(OfferAnswerFailureReason reason, String message, Exception innerException, IEnumerable`1 signalingHeaders, DiagnosticsInformation diagnosticsInformation)

   at Microsoft.Rtc.Collaboration.AudioVideo.MediaSessionAgent.CreateOfferAnswerException(OfferAnswerFailureReason type, Exception e, UInt32 errorCode, RtpEndpoint endpointForDiagBlob)

   at Microsoft.Rtc.Collaboration.AudioVideo.MediaSessionAgent.TerminateAllPendingAsyncResults()

   at Microsoft.Rtc.Collaboration.AudioVideo.MediaSessionAgent.TerminateMediaSession(TerminateMediaSessionWorkitemAsyncResult workitem)

   at Microsoft.Rtc.Signaling.WorkitemQueue.ProcessItems()

   at Microsoft.Rtc.Signaling.SerializationQueue`1.ResumeProcessing()

   at Microsoft.Rtc.Signaling.SerializationQueue`1.ResumeProcessingCallback(Object state)

   at Microsoft.Rtc.Signaling.QueueWorkItemState.ExecuteWrappedMethod(WaitCallback method, Object state)

   at System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)

   at System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)

   at System.Threading.QueueUserWorkItemCallback.System.Threading.IThreadPoolWorkItem.ExecuteWorkItem()

   at System.Threading.ThreadPoolWorkQueue.Dispatch()

--- End of inner exception stack trace ---

   at Microsoft.Rtc.Signaling.SipAsyncResult`1.ThrowIfFailed()

   at Microsoft.Rtc.Signaling.Helper.EndAsyncOperation[T](Object owner, IAsyncResult result)

   at Microsoft.Rtc.Collaboration.Call.EndAcceptCore(IAsyncResult result)

Do you know what causes that exception?

I want to enable Lync Server Centralized Logging Services, which scenario should I run? The AlwaysOn Scenario?

Thank you.