Tree-like Structure in Karamba

Hey guys, I'm a newbie in Karamba and now I'm trying to cross-section optimization in 2D for a tree-like structure in Karamba by using line to beam function.

But, when I put the gravity loadcase, there is no shown deflection. The error message always shows "

1. There are 5 rigid body modes in the system. This means some parts can move freely without causing deformation.
Try to use the 'Eigen Modes'-component and activate the display of local coordinate axes: The first eigen-mode will be the rigid body motion.
If this does not help, check whether you have a pinned support directly attached to a hinge. A hinge introduces an extra node which may cause the problem.
When analyzing a flat shell structure one has to lock the rotation perpendicular to the plate in at least one node."

Can someone help me with this? I attached my GH file if someone wants to spend some time to help me.

Thank you so much!!