Have you tried some examples of the Documentation page? Do they work? What about other "Data" functions, like StarData or so?
There are some 'hidden' functions that look at changes of paclet data like RebuildPacletData, maybe there is some error in your paclet-cache?
Also make sure that all your paclets-sits are up-to-date:
PacletSiteUpdate /@ PacletSites[]
If those don't work, perhaps delete all your paclets in this directory:
ToFileName[{$UserBaseDirectory, "Paclets", "Repository"}]
and try again.