If you are not using Periods (JC Settings, Periods), Job Cost will post entries one month past the current month.
If the entries are dated more than one month into the future they will reject and remain in the new.jct. The month will need to be closed and advanced to within one future month for entries to be able to post.
For example if an entry is dated for October and the current month in Job Cost is August the entry will reject. In order for the entry to post the month will need to be closed to September.
If you are using Periods, then you cannot post past the end of the current period. For example, if you are tracking Weeks and an entry is dated October 7 and you week end date is October 6, you will need to close the week prior to posting.
For more information on closing the month in Job Cost, see How do I close the month in Job Cost?
In Job Cost, how can I tell what the current month is and which months have been closed?
AP transactions are not showing in Job Cost