object not shown in AR after reopening scene?

Hey there,

I have a Question, what happened if I saved my Project and Scene (I have a Vuforia Image Marker and a simple cube on it, it worked perfectly in the Play mode) but after saving and reopening the Scene, the cube is there but is not augmented in the Play mode anymore. This happens all the time, if I delete the cube and add a new one, it works again… but that's annoying :)

what did I do wrong?

Thanks!!