I’ve definitely made both of those methods work, Maybe your .pth file is the wrong format or doesn’t point to the folder correctly. Maybe the thing your pointing to isn’t a valid package, or not compatible with this version of Python or has the wrong architecture. If you use the PsychoPy preferences option then you have to remember to import psychopy before importing the object (because the psychopy pref only gets read when you import psychopy).
Was there an error message when you tried to do the import?