The problem comes with my gradient. It says my two input numbers (lenght of the curves) are failing. I am following exactly the same steps the video shows.
Can’t help you since you didn’t include the file (I also don’t have Rhino for Mac set up), but you’ll at least want to hide your BiArc component, as that preview may occlude the coloured geometry, making it look as though nothing is working.
One thing you can try is convert your text panels with the numbers for the gradient domain into sliders, that at least will tell us whether it is the conversion from text to number that fails, or whether the problem is inside the gradient object.