Let's start by making sure you followed these steps before getting to the Preview screen.
Did you take at least 9 photos before submitting your sequence?
Yes? Then go to number 2.
No? To generate a 3D scan, we will need at least 9 photos in your sequence.
Tip: the ideal number of photos for a face is between 15-20 photos so we suggest aiming for that.
Did you experience any wifi or cell service interruption while your sequence was being processed?
Yes? Resubmit your sequence for processing.
No? Go to number 3.
In some cases, if you try to place your scan by tapping the screen but the phone is too close to a surface behind the phone (such as your phone is resting on a counter or you are holding your phone too close to a tabletop or wall), the object will not be placed.
Truthfully, we don't have a good answer for why this happens but we have definitely experienced it, too. We can overcome this issue by simply moving the phone away from the surface.
Try moving the phone at least 12 inches (or 30 centimeters) above the surface.
You can also just point the phone towards the floor if you're standing. There's plenty of space for placing the scan in the screen for previewing doing that.
If you tapped to preview your scan, but you're only seeing pieces of the scan or what looks like an outline of the scan:
Most likely your scan has loaded backwards. You can use the rotate controls to rotate the scan around until you see the front of it. You may also find that zooming in or out will help you.
To zoom in or out, you can use your fingers to pinch or expand directly on the scan or you will find two magnifier icons for zooming in and out.
If you are unable to rotate or zoom to get a preview of your scan, you may want to use the Reset button. Tapping Reset will allow you to place your scan again on the screen.
If you choose to Reset, be sure to double check that your phone is not too close to any surface (see #3 above to read more about this)