Go to Settings (More tab) and tap "Restore Purchases". If that doesn't work, make sure you're signed in with the same Apple ID you used to purchase the subscription.
Open your iPhone Settings > tap your name at the top > Subscriptions > BiteSafe > Cancel Subscription. Subscriptions are managed by Apple, not within the app.
In the app, go to More tab > Data section > Reset All Data. This permanently deletes all meals, symptoms, and profile data from your device.
BiteSafe uses the OpenFoodFacts database. Some regional products may not be listed yet. You can manually add the meal when a product isn't found. The app will show you the option to "Log as meal manually".