There is a known issue right now we're looking into on Apple devices (iPhone and iPad) that have iOS operating system version 10.3.3. or sooner that cause a white screen (where the app does not load properly). Our development team is currently looking deeper into the issue.
If you or a user at your church has this issue, they will have to utilize the web app or iOS app on another device (computer browser or device with iOS 11+ at this time).
This would affect iPhone 5, iPhone 5s, iPhone 5c and earlier devices.
We're doing our best to resolve this issue. Thanks!