iOS 11 is required for the current version of Stitcher for iOS. Open your device's Settings, then go to General, About, then Version to see what iOS version you're running.
You'll need to update your device's operating system if you're using an earlier version than iOS 13. (OS).
You may find instructions on how to upgrade - https://support.apple.com/en-us/HT204204
Android 6.0 or higher is required for the current version of Stitcher. Open Settings, General, About Device, then Android Version to see what Android version your device is running. If your device is running an older version of Android than 6.0, you'll need to update the operating system.
You may update your Android device by navigating to Settings > General > About device > Software updates > Check for update on select Android devices.