If your app freezes or crashed, the first thing to try is the good old fashioned turn it off and turn it back on again trick. Or, more specifically in this case, hard quit the app and reopen it.
If you are still encountering issues check the following:
- Are you connected to a stable WiFi connection?
- Do you need to update the app in the app store?
- Are other apps also freezing on your phone?
- Is your phone's software updated to the latest version?
If that still doesn't solve it, let us know and we'll take a look behind the scenes. If possible, take a screenshot of the error message and send it to firstname.lastname@example.org along with a short description of what you were doing when the crash occurred.