Is it possible that this job is waiting on input from a DTAQ or MSGQ to fire off the job before going back to sleep? (we have a lot of these Asynchronous jobs here)
Try the WRKACTJOB command and find the job. When you finfd the job in the susbsystem in question, take a 5 (work with) the a 10 (display job log) to look at the job log.
You may find the issue here.
If no explanation is found in job log, the job may need to be restarted.
If it has been up and running since 3/30, without an IPL, it may be some needed files or othe data is no longer available.