did you make sure you were root when you installed it ???
become root, and install the pluggin (to the correct pluggin directory)
then run mozilla from command line (you may need to change permission's of the pluggin)
now, run mozilla from command line, unless you are lucky, you will probably get an error while mozilla is trying to load the pluggin, it might mention it cant find a shared library...
if so, go to www.rpmfind.com
and type in the dependence.so.whatevernumber , and download a package that provides it.