The engine version I'm using (5.6) has not been patched yet so here's a solution to play the game in the meantime:
- Drag the notification bar down and click the settings icon
- Select "Apps & notifications"
- Then "App permissions"
- Select the "Gladiabots" app
- Click the "Permissions" button
- Enable the "Storage" permission
- Restart the game.
Please report here if it doesn't fix the bug on your device.