Why can't calculate Volume or VolumeCentroid of polygsurface

Hi all, I am new to rhino. I just made a polysurface, and I need to find the volume or volume centroid of it, but I get the error

Unable to calculate volume.
or
Unable to calculate centroid.

I tried hours on this, could anyone help? Thanks in advance.1.3dm (1.5 MB)

Hello - when Volume fails it is 99% certain that there is a face in the polysurface for which the Area command also fails. It is tedious but by windowing half of the exploded faces at a time and running Area, you can actually find the bad guy pretty quickly - it is this one:

To fix it, ExtractSrf that face, delete it and Cap the remaining object.

-Pascal