Calibrator Requires Camera Access

Issue:
You can't get past the message: Calibrator Requires Camera Access. In order to calibrate your sensor you need to allow Structure Sensor Calibrator to access your camera. 

Solution:
On your iPad/iPhone simply go to:

Settings

In the left pane, scroll down until you find Calibrator:

Tap Calibrator. In the right pane, you will see all of the permissions Calibrator needs. Toggle the Camera permission to "On".