While activating Mac Screenwriter 6.5 or Dramatica Story Expert 5.3, did you get an error 123, "ActivationParamLocaleNotSetError" Missing required DefaultLocale param?
This error, which is very rare, happens when you haven't set the proper locale (country/location) on your Mac. For example, you are in Canada, but your locale (i.e. Language & Region) is set to "United States".
Try setting it to Canada, then re-try activation.