failed "Cast to ARTrackedImage"

Following the AR-Image Detection Tutorial by Joe Graf ( we implemented the Blueprint at the bottom of the Page inside the BP_ARPawn of a fresh AR-Project Template.
The target image is also taken from the above Tutorial. During runtime something gets detected when targeting the target image, but the “Cast to ARTrackedImage” fails, thus no actor is spawned and the detection fails.

Screenshot of Blueprint is attached.

Any ideas on how to fix this?