I'm having the same issue.Yum reports that nsplug* is installed, however I noticed that the "/mozilla/plugins-wrapped" sub-directory is populated with other plugs. I also noticed that there's no executable "nspluginwrapper" - I searched and couldn't find it[?]. I'll try un-installing it and then do a re-install.
On side note: This is the single most important plugin and with a growing number interested in Linux, it's sad that Adobe/Flash hasn't advanced the install process! I realize it comes down to $ and perhaps after 1000's of people complain maybe they'll streamline the installation. Until terminal commands are eliminated for install, issues like this will discourage new users... [stepping down from soapbox]