Symptoms
Workflow did not start according to the SharePoint Listener Events configured. Unable to access the RemoteEventReceiver site at our end.
Diagnoses
When new Sharepoint List items are added. Customer notice that the workflow instance not fired in accordance to the Sharepont Event listener configured in the worklfow
Resolution
Upon checking on RemoteEvent Service in IIS (under K2 Website -> SP15EventService -> RemoteEventService.svc) not accessible. Sharepoint 2013 will call this service to initiate any instances in Blackpearl server. Resolved after customer disable the ASP.Net impersonation of SP15EventReceiver site in IIS.