Issue description
Rainbow Android App automatically closes on start when managed by a MDM (Mobile Device Management) system.
Root Cause
MDM systems can push configuration files to the app. It's called AppConfig. Your MDM probably send an empty AppConfig file.
How to fix the issue
You need to configure your MDM to stop pushing configuration files to the application.
For mobile where the faulty installation was already made, uninstall the Rainbow Android App and reinstall it without sending the AppConfig file.