Found what I was doing wrong. I needed add a WHERE clause at the very end of the query, outside of the parenthesis.
select jo.jobnum
,cast(jh.duedate as varchar(25)) as duedate
,jo.oprseq
,jo.description
--,jo.duedate as OpDue
,jh.partnum
,jh.revisionnum
,case when jh.jobclosed = 1 then...