Non-convex to convex

I’m following @Mackay 2014 HB tutorial video “10 - Honeybee Energy Modeling - The Laws of Geometry in E+ Part 2: Core+Perimeter Zoning” on youtube. I downloaded the asssociated GH file.
I’m using HB_Legacy 2020.
I successfully made floors and perimiter-core zones on the rectangular tower. But when I try to do the same for the other shape (the one with inward curving surfaces), I get the error “You have a non-convex (or faulty) geometry, and this component mainly handles convex geometries (at this point). You should prepare the massing of your building by dividing it into convex volumes before using this component”. My work process is show in the image below. What is the most direct way to convert non-convex geometry to convex geometry in Honeybee?
I tried using GH FMerge but it didn’t help.
Thanks for helping.

Same issue, i tried lots of ways but not solve it