I have tested the app on an iPhone 7 and an iPad Mini4 (both running IOS 12.1) and on a Samsung A5 with Android 7.
Calibration won’t work on both. On Android, I get a message ‘Error during configuration’. On IOS I got simply no response. Just the option to tap on Cancel or Ignore.
Tapping ‘Ignore’ on IOS runs (literally) through the calibration steps and then states ‘Calibration successful’ which it is obviously not.