What Android version are you running? Unfortunately the latest Android build coupled with certain specific phone models prevents Ren'py games from working.
If freeing up space and restarting your phone hasn't worked - and the issue lies with the Android build and phone model - then you can try installing "JoiPlay" from the Google Play Store ( https://play.google.com/store/apps/details?id=cyou.joiplay.joiplay ) and install the PC version of the game. It works exactly the same as the Android version.
Good luck! And sorry for the inconvenience :(