It is possible that the plug-in has not been scanned correctly.To force a re-scan of the plug-in, do the following:

• Go to Logic Menu and go to Settings > Plug-in Manager.
• Click Full Audio Unit Reset.
• Restart Logic. It will re-scan all the available plug-ins, then the plug-in should now show up in the list.

If problems persist, quit Logic, open Terminal in your Applications/Utilities folder and type the following command

killall -9 AudioComponentRegistrar.

Then restart Logic.