Hello Laurent,

Thank you for using our toolbox. We hope you find it useful.
Regarding your problem. In the modal window of the Step 2, after click on Preprocess model button and generate the fitted curve, the modal window is minimized to see the results. So, you have to maximize it and click on "OK" button of the modal window (attached file) to accept the preprocessing results before continue to Step 3 Pixel-wise Calculation.

If you have any more problems, please let us know.

Regards,

Jose