It seems that you're referring to the auto mileage tracking on the app. Let me help you.
The first thing we need to make sure of is that the app is updated. Visit the App Store or Play Store and update it from there. You also want to upgrade your device's operating system so it'll be compatible with QuickBooks Self-Employed. If the same behavior persists, I'd recommend uninstalling, reinstall the app.
Here are some of the articles you'll want to check. These will discuss more on how to fix issues regarding mileage: