Items in sleep status does not wake up

I have this code

   foreach(SourceCode.K2ROM.WorklistItem oWorklistItem in oWorklist)
   {
  
    if((oWorklistItem.ProcessInstance.Folio == itemOrdNo)&&((oWorklistItem.ActivityInstanceDestination.Name.ToString().IndexOf(itemActivity))!= -1))
    {
     oWorklistItem.Sleep(true,20);
     oK2Connection.Close();
     break;
    }
   } 

 This code works in my testing environment. But in another enviroment the items that where set to sleep mode does not wake up even after 20 sec expiration. Please help. This has been bugging me for days already. Any ideas would be appreciated.