It's possible that abstracts from these years didn't survive to be microfilmed or just didn't exist in the first place. Everything should have been microfilmed, but there are definitely gaps in these early records. Sometimes the page that identifies the date is missing, and these abstracts are filmed at the end of the rest for that port. But that doesn't seem to be what's happening in your case. The most likely scenario is that they just didn't survive.
(National Archives staff)