My Kindle app has stopped working. First sign of trouble was about two weeks ago. I was on a plane and wanted to read a book. Plane had no Wi-Fi. When I first tried to read the book, the Kindle app told me I needed an internet connection. I shut down the app once or twice, and I may have rebooted the Surface, and I was able to use the Kindle app for several hours after that. This week I had another flight and tried to use the Kindle app for the same book. This time I was unable to get the app to stop telling me I needed an internet connection. All it would do is to post that message. I could not get to the library. Now that I am back in Wi-Fi territory, the app displays only a black screen, no message, not nothing. getting rather annoying. I have books I paid for and cannot read! What do I do next? Thanks.