The plugin files may not be in the right location. On a PC, they need to be in C > Program Files > Common Files > Digidesign > DAE > Plugins. On a Mac, they need to be in the Mac HD > Library > Application Support > Digidesign > Plgins. If they are not, search your computer for them, then copy them into this folder. On boith platforms, the file you are looking for will be called Autotune.dpm. There may also be an Autotune.dpm.rsr file to copy over, too.
Lead PC Install/Repair Tech
Sweetwater Service Dep't