AE is not seeing plugin folders that are in the correct folder.
Example:
How to install Normality fo AEcs5?
Path with folder:
C:\Program Files\Adobe\Adobe After Effects CS5\Support Files\Plug-ins\Effects\minning.de Normality\mi_Normality3.aex
Folder is not seen in AE, Plugin is not seen in AE
Path
C:\Program Files\Adobe\Adobe After Effects CS5\Support Files\Plug-ins\Effects\mi_Normality3.aex
plugin is not seen in AE
Applying Normalityin After Effects