I am running SDP (free edition) ver.: 9.0 Build 9041

I am running query below:

SELECT qd.QUEUENAME "Group",qd.QUEUENAME "Group",wo.WORKORDERID "Request ID",longtodate(wo.CREATEDTIME) "Created Time",longtodate(wo.RESOLVEDTIME) "Resolved Time",wo.TIMESPENTONREQ "Time Elapsed",std.STATUSNAME "Request Status",aau.FIRST_NAME "Requester",wo.TITLE "Subject",ti.FIRST_NAME "Assigned Technician" FROM WorkOrder wo LEFT JOIN SDUser sdu ON wo.REQUESTERID=sdu.USERID LEFT JOIN AaaUser aau ON sdu.USERID=aau.USER_ID LEFT JOIN WorkOrder_Queue woq ON wo.WORKORDERID=woq.WORKORDERID LEFT JOIN QueueDefinition qd ON woq.QUEUEID=qd.QUEUEID LEFT JOIN WorkOrderStates wos ON wo.WORKORDERID=wos.WORKORDERID LEFT JOIN SDUser td ON wos.OWNERID=td.USERID LEFT JOIN AaaUser ti ON td.USERID=ti.USER_ID LEFT JOIN StatusDefinition std ON wos.STATUSID=std.STATUSID WHERE (wo.ISPARENT='1')  ORDER BY 1 NULLS FIRST , 10 NULLS FIRST

 Why I got “00:00:00” “Time Elapsed” although there are some requests are RESOLVED and CLOSED state (see enclosed screenshot), what I missed?