@chuazy Sometimes this can happen in the Calibrator App if you haven't inputted or chosen the right case that you are using with the Structure Sensor to affix to your iOS device.
The Calibrator App needs to know exactly where the Structure Sensor is positioned from the iOS device's color camera in X, Y, Z offset to correctly overlay the depth image from the color image. Please make sure that you are selecting the right case within the Calibrator App. If you have a case that is not an option, please choose the color case option and correctly input the X, Y, Z coordinates.
From the image you sent over to me, it looks like the scene is complex enough, but does not have enough sunlight, as most the image is in shadow. Please make sure that you are choosing both a complex and well-lit scene during calibration.
Please let me know if this helps!