If your app freezes, force close the app and re-open the app.
FLY iOS APP
Double click the home button and swipe up to close the app. Then re-open the app.
FLY ANDROID APP
Tap your Recent Apps button to bring up the list of all recent apps. Swipe to close the Fly app. You may also visit Settings and select your app settings. Android devices have a section in settings to manage apps which you can use to close open apps.