All payments are handled exclusively by Apple and Google, so when you tap the "start now" button, our app calls the Apple (or Google if you are on android) system to enable the payment. All those alerts are from Apple and linked to your iTunes account. If something happens there, you should check the status on your App Store profile.
If you are a subscriber and you have re installed the app (or update it), you will see the welcome and payment screens. If you tap the start now, the app will recognize you as new user and the payment will fail. So you must tap "Restore purchases" on the top right corner.
Restore purchases is also located on the app under "settings" (the gear icon collocated on the right top square)
