As a SketchUp user, have you ever modeled an object and cannot find its volume?  It can be frustrating, but in SketchUp, a “Solid” will not report a volume if there is any errant geometry in the group or component.  This could be an extra line or something out of place that can really be hard to find.  ThomThom created an awesome plugin called “Solid Inspector” (along with many others) – check out this video to see how we use it and why we recommend the plugin.