The first thing to do is make sure you are signed in to your Planta account and that your Planta app is updated to the latest version. If you are already logged in, log out and completely close the app, then re-open it and log back in.
If you purchased your subscription in the app:
- Log into your Planta account
- Tap the Settings button (gear at the top right corner)
- Tap "Account"
- Tap "Restore Purchases" to sync your Planta account with the premium subscription
If this doesn't help try to force close the Planta app