Outlook interop service is not working in windows task scheduler

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C#

I have developed a console application to create OUTLOOK meeting requests. It is perfectly working fine when Im running it in Visual Studio. But when I schedule it in the Task Scheduler, it does not work. It gives me the bellow error.

Error : Operation unavailable (Exception from HRESULT: 0x800401E3 (MK_E_UNAVAILABLE))

below is my code.

public MeetingDVO sendOneTimeMeeting(MeetingDVO dvo)
   {
       log.Info("In side Send Onetime Meeting");
       object outlookObject = null;
       Outlook.Application oApp = null;
       Outlook.AppointmentItem agendaMeeting = null;
       Account acc = null;
       string status = string.Empty;
       try
       {
           outlookObject = Marshal.GetActiveObject("Outlook.Application");

           if (outlookObject != null)
           {
               log.Info("Marshal Object Created");
               oApp = new Outlook.Application();
           }
           else
           {
               oApp = new Microsoft.Office.Interop.Outlook.Application();
           }

           if (true)
           {
               log.Info("creating outlook Object");
               //oApp = new Outlook.Application();
               //oApp = CreateOrAttachToOutlookApplication();
               log.Info("Object created");
               agendaMeeting = (Outlook.AppointmentItem)oApp.CreateItem(Microsoft.Office.Interop.Outlook.OlItemType.olAppointmentItem);
               log.Info(" agendaMeeting Object created");
               acc = SetAccount(oApp);
               log.Info(" Account created");
               if (agendaMeeting != null)
               {
                   log.Info(" in side Account IF");
                   Outlook.NameSpace nameSpace = oApp.GetNamespace("MAPI");
                   log.Info(" Namespace");
                   agendaMeeting.MeetingStatus = Microsoft.Office.Interop.Outlook.OlMeetingStatus.olMeeting;
                   agendaMeeting.Location = dvo.Location;
                   agendaMeeting.Subject = dvo.Subject;
                   agendaMeeting.Body = dvo.Body;
                   agendaMeeting.Start = dvo.TimeSlot;
                   agendaMeeting.Duration = dvo.Duration;
                   //agendaMeeting.RequiredAttendees = "skoswattha@emaar.ae;KCornelio.dul@emaar.ae";
                   agendaMeeting.RequiredAttendees = "skoswattha@emaar.ae";
                   //agendaMeeting.RequiredAttendees = "skoswattha@emaar.ae";
                   //agendaMeeting.ForceUpdateToAllAttendees = true;
                   //agendaMeeting.ResponseRequested = true;
                   ((Outlook._AppointmentItem)agendaMeeting).SendUsingAccount = acc;
                   ((Outlook._AppointmentItem)agendaMeeting).Send();
                   dvo.EntryID = agendaMeeting.EntryID;
                   dvo.Remarks = MeetingSucess;

               }
               else
                   dvo.Remarks = MeetingError + " : " + "Meeting Object is Null";
           }
       }
       catch (System.Exception ex)
       {
           log.Info(ex.InnerException +":::::: MESSAGE----"+ex.Message);
           dvo.Remarks = MeetingError + " : " + ex.Message;
       }
       finally
       {
           oApp = null;
           agendaMeeting = null;
           acc = null;
       }

       return dvo;
   }

any suggestions?