Why does aggregator report "There is new syndicated content" but still 0 items for this feed? We've had a working feed aggregator running for quite some time now (over 12 months) from a YouTube feed link (http://gdata.youtube.com/feeds/base/users/[username]/uploads). We just recently noticed that there are no items displaying in this feed's block. Upon visiting the feed configuration page (admin/config/services/aggregator/edit/feed/[feed-id]), I can see that there are 0 items in the feed. Running the feed manually reports "There is new syndicated content from YouTube.", but there are no items created. The dblog shows an entry from the feed aggregator with the same message, but no error messages. 

Has anyone experienced this or have any ideas on where to troubleshoot? Without any actual errors I'm unsure if this is a bug, works-as-designed, or potentially something wrong with YouTube's feed. I've validated the feed on a couple of websites and there are no (apparent) issues with it.
I have just been experimenting with the aggregator and come across the same issue. The only workaround that I have been able to find in order to pull content from the RSS feed in issue has been to use the Feeds module. If you are still having this issue then this is a possible solution.

EDIT: Just found a far simpler solution for the problem. By default the aggregator deletes items older than 3 months and 3 weeks from the feed. If the youtube feed you are subscribing to has not had new content added in that time then you may get the situation you describe. If that is not the case then go with the first option I suggested. Otherwise you can change how long Drupal keeps the feed items in the Aggregator settings tab.