The black H is what the yellow/green square dot used to be. No symbol is what the zzz symbol used to be. Essentially, it's just a confusing non-change.
If you see a title in your list that has no symbol next to it, it means that is not "featured" as per the Hubpages definition of "featured." Meaning that your hub has the no-index meta tag and that search engines will not index it. In that case you can either unpublish it and post it elsewhere or make some minor edits to put it back into pending. After 24 hours it will either be featured again or remain unfeatured.