Ask for help, numerical resolution of Richards equation using Van Genuchten model

Hi everyone ! I am working on predicting pressure head using Richards equation. I recently read about SimPEG and I tried to run some examples from
my problem is when I tried to change the parameters from Haverkamp model to Van Genuchten model (initial and boundary conditions from celia1990), the output seems to be constant and equal to the initial condition. Thank you in advance.

My best guess on this would be to check the units of your VG model, and make sure that everything is consistent. It is possible that the celia model was in cm in the mesh?

If you hydraulic conductivity is off by a few orders of magnitude that could explain it?!

Best of luck!