WineRatings+ is a free download, but access to the wine reviews requires a monthly subscription, involving what is known as an "in-app purchase." Before we can process your subscription for an iPhone or iPad through the App Store, you need to change your device settings and enable in-app purchases.
From your device's home screen, please go to Settings, then General, then Restrictions. Scroll down to the section for "Allowed Content." There you can toggle In-App Purchases from "Off" to "On," to allow subscriptions.