I think I made this by just extruding a cirlce, then I offset the outer surface inward to create this final shape (solid=yes). When I run the Volume command, I get this:
Calculating volume… Press Esc to cancel
Unable to calculate volume.volume_error.3dm (147.8 KB)
I don’t need a work-around, I rebuilt it and got what I needed. Just reporting the odd error, thx.