Hi Randy.
I think Charles is correct about the blank field being your issue. I have done this one myself. But keep an eye on the jobs periodically even if this fixes your issue.
I have a mix of scheduled jobs on my systems, some with no expiration as you are doing and some with expirations. This is to address an unpredictable issue I have encountered where jobs with no expiration just stop scheduling. I can update the job without making a change and it will create the next 5 jobs and stop again. Or things will return to normal for that job. Very odd and very infrequent.
Good luck!