Trackable StoneTarget NO_POSE -- UNKNOWN

Hello everyone! Created a mini AR programm, when you click on the play, it displays the following message: “Stop Vuforia Engine” and “Trackable StoneTarget NO_POSE - UNKNOWN”. Any help would be appreciated.

i am having the exact same issue. i have tried with three different objects. my points on the objects range from 100 - 300. i have tried different lighting. I do not believe the issue is the object. I have also tried with three different low poly models. Those arent the problem either. It is interesting that they disappear from the scene in play mode (unless this is normal, i am fairly new).

same here…out of suddent this error come out…really frustrated