Creating buildings from footprints using dragonfly

Im stuck on creating buildings from footprints,
I keep on getting a warning that on the image attached to this email.
Any help?
(also since im a new user it wont let me upload the file)
Kind regards

Hi. Trying using project to c plane command to flatten the curve and make them co planner.

how do i do that

Use project to cplane command and also check that no closed polyline intersect each other.

it says unable to project all the objects