Apple ended support for iOS 7 in August of 2014. As a result, Avi-on has dropped support for that operating system because we are unable to get the tools from Apple that we need to make a great app. As of Avi-on version 1.4.0 or later we no longer formally support iOS 7. It may or may not work on your device, but you will likely see unpredictable behavior and screens may not render correctly.
Please upgrade your Apple device to iOS 10 or higher.