I downloaded Nikon Studio version 1.6 and was able to launch it from Photo Mechanic 6 using MacOS. When launching an editor, Photo Mechanic doesn't really know what it is launching, you simply point it to an executable and it asks the system to open the selected files in that app, so I can't see why the version of Nikon Studio that you are launching could matter. If you revert back to version 1.5 does it start working again?