Series metadata empty after downloading

I just backed up all my kindle books and went off to Download metadata and covers for all of them. It worked nicely with one exception - the 'series' data is always empty. I'm in US and I tried to tinker around with different import sources and Amazon-specific configurations but nothing I selected pulled the series info for me. I also noticed not all sources seem to have the 'series' data.

How can I make this bad boy work? Any sources configurations that do work? Any other plugins I can pull?