This often occurs when permission to use the camera has not been granted from the device.
For iOS (iPhone & iPad) devices you can go open settings app on the device Then scroll to find Battery Steward and tap to see the permissions set by the app. Check to see if camera permission is selected.
For Android devices go to settings, find and tap on Application Manager. Scroll to find the Battery Steward app settings. Tap on permissions in the Battery Steward app settings.Check to see if camera permission is selected.