If your payment went through successfully and yet the app does not show PRO features (this is easily tested since there will be "PRO" next to the Delta symbol) or shows an error code: 32459, here's a quick way to fix it:
Force close the app and re-open it.
Go into settings in the app and tap the "Restore Purchases" option. This should fix it!
In rare cases, if that doesn't work, please re-install the app, and use the same "Restore Purchases" button, and if it still doesn't work, let us know!