I have been having this issue in Vuforia Studio where the spatial target is picking up the ground plane, showing where the model "would" go, saying "tap to place" under the model. I try to place the object but it does click. My first thought was that the model was too big, so i scaled it down to 10%, but it still didn't place. I checked my app to make sure it was the current version on both the PC and mobile device. Please let me know what to try next!