I do not know what has gone wrong, but I do know how to make it work.
The camera has Automatic Gain Control (AGC) to attempt to take the best broad picture.
As the picture is mostly black, it winds the gain to the maximum - thus causing the picture to flare.
Solution
Add a piece of A4 (or office size paper) next to the calibration card. The camera will recalibrate against the new ‘white’ surface and the calibration will now work.