OPPO dropping out of gospel library app

Has been working fine and suddenly stopped on my mother's phone on Tues/Wednesday - I uninstalled and powered down the phone but it flashes up on the screen and then shuts down - reinstalling isn't working either, it just keeps trying to open from the play store but not showing as installed on the main phone screen with the other apps, please help as it is Sunday tomorrow

Does the device have any system updates available that need to be installed? You could also check to make sure that Google Play Services and the Chrome webview are up to date.