Help with unconfined aquifer!

Hi guys, I try to do a model with the new unstructured mesh, but when I configure the problem of the model in unconfined aquifers in the problem class, I can't activate this option. Can you help me with this?
Thanks.

Models with partially or fully unstructured meshes allow the representation of confined conditions or unsaturated flow (Richards). The simplified free & moveable method and the phreatic approach is not available.