I tried both call webservice in Nintex Workflow or program call the webservice directly .
There is no problem for the GetRunningWorkflowTasksForListItem(query). But we always have 500 Internal Server Error for ProcessFlexiTaskResponse(update).
I have tried two Account: My Account(cn-xucry) and Service Account Sharepoint.
Another Account BPM_Service report “403 unauthorized error”.