Webcut a volume with a sheet body


I am trying to webcut a volume with a sheet body using the following commande :

webcut Volume 3 tool Body 10  

but I get the following error :

Performing webcut operation…
WARNING: Cutting Sheet does not intersect the original volume.
The original volume is restored.
No volumes were webcut.

However, my sheet does intersect the original volume.
I have also tried with the command :

webcut volume 3 with body 10

Unfortunately, I got the following answer:

Performing webcut operation…
No volumes were webcut.

The volume I am trying to webcut is created like this:

# topo_surf.sat is a surface representing the topography import "topo_surf.sat" create planar surface with plane offset -500000 create volume loft surface 1 2

The sheet body is made of several stitched surfaces.
You will find in attached file a a screenshot of my geometry.
Do you know where the problem could come from?
Thank you in advance for you answer

Best regards,