Error in 3D meshing of a Kelvin cell

[JohnPsih]

Hello, I want to create a 3D mesh for the kelvin cell (STEP and geo file are imported below). But I get the following errors.
No elements in volume 1.
The problem may be that the kelvin cell is not a closed volume. What can I do to be able to create a 3D mesh?

Kelvin_cell_text_11.txt

Kelvin_cell_one_body_GEO.txt