I posted an issue previously about iOS 11 and vitoria not working. Ive recently tested my app on an iPad with iOS 10.2 and it still did not work. 

Here are the versions of apps I'm using

Unity - 5.5.1f1

Xcode 9.0(9A235)

Vuforia - 6.2.6

Here is the error:

Exception in callback: System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.NullReferenceException:

  at UnityEngine.Behaviour.get_enabled () [0x00000] in <filename unknown>:0

  at Vuforia.StateManagerImpl.UpdateTrackablePoses (UnityEngine.Transform arCameraTransform, .TrackableResultData[] trackableResultDataArray, .VuMarkTargetResultData[] vuMarkResultDataArray, TrackableIdPair originTrackableID, Int32 frameIndex) [0x00000] in <filename unknown>:0

  at Vuforia.VuforiaManagerImpl.UpdateTrackers (FrameState frameState) [0x00000] in <filename unknown>:0

  at Vuforia.VuforiaManagerImpl.Update (ScreenOrientation counterRotation, Boolean reapplyOldState) [0x00000] in <filename unknown>:0

  at Vuforia.VuforiaARController.UpdateStatePrivate (Boolean forceUpdate, Boolean reapplyOldState) [0x00000] in <filename unknown>:0

  at Vuforia.VuforiaARController.UpdateState (Boolean forceUpdate, Boolean reapplyOldState) [0x00000] in <filename unknown>:0

  at Vuforia.DigitalEyewearARController.Update () [0x00000] in <filename unknown>:0

  at System.Reflection.MonoMethod.InternalInvoke (System.Object obj, System.Object[] parameters, System.Exception& exc) [0x00000] in <filename unknown>:0

  at System.Reflection.MonoMethod.Invoke (System.Object obj, BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x00000] in <filename unknown>:0

  at System.AppDomain.add_UnhandledException (System.UnhandledExceptionEventHandler value) [0x00000] in <filename unknown>:0

  at System.Reflection.MethodBase.Invoke (System.Object obj, System.Object[] parameters) [0x00000] in <filename unknown>:0

  at System.Delegate.DynamicInvokeImpl (System.Object[] args) [0x00000] in <filename unknown>:0

  at System.MulticastDelegate.DynamicInvokeImpl (System.Object[] args) [0x00000] in <filename unknown>:0

  at System.Delegate.DynamicInvokeImpl (System.Object[] args) [0x00000] in <filename unknown>:

Vuforia is loaded into a scene that persists through out the app while other scenes are loaded in and out. When a new scene is loaded in and the old scene is unloaded is when the app breaks on device. This issue does not occur in Editor.