Might try logging in as the Host, go to the Search Admin function and click on the re-index content link.  The syndication features are tied to the DNN Search functions.  Also, check out the Scheduler functions, and ensure that the jobs are enabled.  The first is supposed to perform a purge of the cached items, removing any expired or deleted items, and the second is to perform a scan for new items.  Both have pretty flexible schedule times, so play with those settings to get the results you need.

DotNetNuke.Services.Cache.PurgeCache, DOTNETNUKE

DotNetNuke.Services.Search.SearchEngineScheduler, DOTNETNUKE

As a general rule, I've always had to re-index content after adding items that I want to make sure get syndicated.  I think there are some issues with the schedule and search functions, but I'm not certain.  I just know that's been my experience.

See if that helps at all...