When a patron places a hold, then suspends it, and later unsuspends it, the hold will not show on the Holds to Pull list unless the date is set to include the original hold date. This date range is controlled by the system preference HoldsToPullStartDate. When you leave that system preference blank, the system still defaults to 2 days. Libraries should have the option of leaving the system preference blank to show ALL holds that need to be pulled regardless of the original hold date.
This may meed deeper investigation. We think the problem more than just the Holds to Pull report. It's much bigger than that. The system should consider the hold to be active after it is either manually unsuspended or it reaches the end date of a suspension. We see that the circulation side of Koha simply does not indicate the hold status at all - it is not shown as on hold or hold pending on the staff side, but the OPAC does show hold pending, not available.