One subscription works across all devices, but you need to create a UAVForecast account and log into it from all your devices in order for this to work, as explained in the app next to the purchase button. Apple's non-renewing subscriptions do not automatically transfer to other devices and refreshing purchases on another device will not automatically activate your subscription on that device too. You need a UAVForecast account because the subscription information has to be uploaded to our servers for this to work.
When you purchase a subscription on iOS, you need to create a UAVForecast account, otherwise if you upgrade your device or lose your settings, your subscription may be lost. This is explained after making the purchase. If you did not do so, or if your subscription should be valid but not showing correctly, please contact firstname.lastname@example.org and let us know your device ID(s) (from the Settings tab), and include a copy of your iTunes receipt(s), and we'll try to fix it for you. Thanks!