Scanything calibration

Please help:
We cannot get Scanything to calibrate. We have used it a few times successfully but today we cannot get it calibrated. The camera seems to be orientated correctly and it locks onto the central dot. It does the 4 corner thing but on the transverse scan it moves to the right and then left and then simply stops. We have tried everything but cannot get it to calibrate.
Any suggestions or help would be greatly appreciated!