Apple currently uses the Apple ID and the iCloud account to manage in-app purchases and subscriptions.
All transactions are bound to your Apple ID, so you can restore them easily. iCloud is also used to manage subscription cycles and expirations.
As a general rule recommend using the same email account for both your Apple ID account and your iCloud account to restore purchases easily on any iOS device.
First, do the following to restore your in-app purchase or subscription:
1) Open "Weather Now" app
2) On the navigation bar tap to "Settings" icon
3) Go to the "INFO" page and tap to the "Restore Purchase" string.
4) The app will connect to the Apple server and will restore your purchase/subscription.
5) Done, the purchase or subscription is restored and you can use the Premium version of the app.
If you see the pop-up window with the message "Transactions doesn't exist"
1) Check your Apple ID, it's must be the same as what you used when made the purchase. If you use a few Apple IDs on your device, you must use only Apple ID what used when made the purchase.
2) Find your purchase in your purchases history ( all purchased is assigned with your Apple ID) How to do it, read here: https://support.apple.com/HT204088
If you can't find the purchase at you purchases history, it's mean what you a never purchased the Weather Now for this Apple ID.
If you are thinking what it is wrong and you are sure what you made the purchase and paid for that, please contact with Apple, because only Apple can find your transaction, they don't share the purchase and transaction information to developers.
Please use this link for contact with Apple: http://reportaproblem.apple.com/
If you have the purchase information and you can't restore purchase and still see the message "Transaction not exists", please contact us.
Please attach the proof of purchase - screenshot from your purchase history with full information about the purchase: date, purchase id, app name, purchase name and etc, or email from Apple Appstore with purchase confirmation and send this to our email firstname.lastname@example.org