Thank you for your post! With the new release of version 3.6 of the application, we have dropped support for older versions of the Android operating system. The application is only compatible with devices running Android 6 and higher. If possible, can you update your operating system? To do so, please go to the Settings app on your device and tap Software Update to ensure you’re running the highest version available for your device.
Let me know if you have any further questions.
All the best,
Avenza Systems Inc.