I've had the exact same problem, got a Samsung S8 when it was released a few weeks back. I had a iPhone before and never had a problem but now I'm having to reinstall the game every day. It'll work for a day and then when I get up each morning It'll close down on start up. This is the advice that square sent me but none of its worked-
Close all other applications running in the background, and turn off any high-power-consuming wallpapers.
- Delete your web browser?s history, cookies, and cache.
- Since errors are more likely to occur when devices have little free storage space, please consider removing any unnecessary apps, images, sound/music, etc.
- Try turning off your device for a few minutes, and then restarting it.
- Please consult your device manufacturer or provider for more details on device troubleshooting