The Problem List is used to generate claims for overdue or skipped items.
All regular serials claiming is done through the latter list.
You will need to switch back and forth between the two. Be sure your search won't retrieve too many entries or the Acquisitions module will hang and crash. As you remove items by claiming them, the records beyond 75 will appear. Voyager is inflexible about expected dates. Many of the items that appear on the Problem List as being expected can be postponed for a month or more to allow for shipping problems, volumes received out of order, etc.