Modifying Solids

Hello community,

Why when I'm using the OpenBuildings Software when I try to modify solids I always get the below response? I thought this software was supposed to make my life easier, not make me want to cry ha. 

The Feature: "Difference #39" cannot be created with current settings and geometry.

Can someone please help me. What settings and geometry do I have to use / change to be able to use these features?

Much appreciated in advance.

Cheers, Jack.