It’s a weird paiting procedure, that’s for sure!
I got mine to work, I put up a couple videos (here’s one and the other is linked in the description of this one)…
When you calibrate you’ll want the calibration grid to be totally vertical and I find it works best to try to make it fill the red rectangle as perfectly as possible. I would suggest against messing with the phone while it’s doing any scanning as I’m assuming the camera won’t function unless the app is in the foreground. Also, prevent the phone from turning off the screen as that seems to mess it up too. It doesn’t seem like they’ve implemented a way to inturrupt a scan, so unplugging it might be the fastest way to make it give up if a scan or calibration is surely not going to work.