The only way I could fix the exact same problem you describe was to completely un-install Amazon appstore, and then re-purchase iReal from the Play store. Personally, I didn't have the time or the patience to discuss a refund with Amazon appstore. And lucky for me, I didn't have anything else from Amazon appstore that was crucial to me. It's been about 2 1/2 months since I've been using IReal purchased from the Play store and there haven't been any problems.