How to buy a lifetime purchase
Buying the lifetime version of Previs Pro is different than buying the monthly or annual subscription. Apple doesn't let you buy it through normal Subscription channels. But it's still fairly easy.
If you are in a trial or a paid subscription (monthly/annual), then you must first let this subscription completely end.
Don't worry! Your files or storyboards are not lost. Everything remains.
After your subscription has expired, start Previs Pro. Then you will see a screen including the option for the lifetime purchase of Previs Pro.