On OS X the VocALign Plug-ins are installed in the folder
In Studio One open the menu item
Studio One -> Preference
The preference panel will be displayed, select the tab Locations -> VST Plug-Ins
Make sure /Library/Audio/Plug-Ins/VST3 is listed as a location.
Make sure Scan at startup is selected.
Select Reset Blacklist
Then close the dialog box and restart Studio One.