Split and boolean difference both failing - Duplicate topic

Hello, I’m trying to see what a dome roof would look like on my project, but Rhino is preventing me from splitting objects or even using boolean difference saying “Split failed, objects may not intersect or intersections may not split object.” I don’t know what to change to make this command work.

Inserting the file here for a closer look.
RHINO DESIGN III.3dm (15.9 MB)

See Problem with split and boolean difference