Certain feeds stop surfacing new items after a while. It might be a problem with datestamp formats. Here’s an example: NewsBlur’s top item showing for http://gizmodo.com/author/mat-honan.xml is a month old, while the xml file shows posts up to today.
Account: gazuga on dev.newsblur.com.
Right click on the site and go to Statistics. What are the times shown there? Also, if you Insta-fetch Stories on a site, it will kick-start it, although there are a number of automatic protections from sites falling through the cracks, so that should not be necessary at all.
Ugh, this was a rough one. Turns out Gizmodo is giving an HTTP error code because I have “Safari/XXX” in the user agent. Removed that and it now works fine. See this commit for details: http://gizmodo.com/author/mat-honan.xml
Mat’s XML file? 
It’s because the feed is giving invalid IDs. The publisher needs to fix that in order for new stories to be recognized as unique stories. What this feed is effectively saying is that each story is just a rewrite of another story.
Makes sense. Wonder if this is a standard behaviour of the Blogger CMS if you don’t title your posts. I’ve emailed the authors.
Yeah, let me know how that turns out. I’d love to get this working.