Apple made changes in iOS 7 that affect OnSite.
1) When you restart your phone, you must open OnSite to start location tracking. This includes the restart that is part of upgrading iOS.
2) To maintain location tracking, don’t kill the app. You can verify OnSite is running by double clicking the home button and swiping through your running apps.
3) Verify OnSite has permission to run in background. Got to Settings -> General -> Background App Refresh. You should see OnSite in the list of apps with the switch set to green.