Pro Features not unlocked after purchase
When you have purchased the Pro Features you can always restore them using the Restore previous purchase button in the purchase dialog.
If restoring does not work, you can also just purchase the Pro Features again. As the Pro Features is a one time, non-expiring purchase, you will not be charged again.
Please note that Mac and iPhone/iPad purchases are separate as they come from different App Stores and have different prices. On a Mac you can only restore Mac purchases, on an iPhone or iPad you can only restore purchases made on an iPhone or iPad.
Some users reported problems with purchases not being unlocked correctly on macOS High Sierra. If restoring the purchase does not work on your Mac, please try to delete the Wokabulary app and re-install it. (On the Mac vocabulary data is stored separately from the app, so this will not affect your data).