So, I recently paid $4.99 for the in-app purchase in order to pay the sound indefinitely. But, after upgrading to iOS 11, I've find that I can't open the app at all. It's been almost two months, add the app developer apparently is not interested in further supporting this app. It appears that he's released another version under the same name, but you cannot restore your purchase within this app on that app. Seems quite shady to me and very disappointed. Caveat emptor - buyer beware!