I think the trouble is the use of the term "SubD". What we generally mean is a polygon mesh that has been subdivided (aka "smoothed"). It remains a polygon mesh, just with more polygons and averaged vertex positions. It's not a true subdivision surface. To subdivide your mesh, use the mesh>smooth option, or hit "3" on your…
Does the script editor give you any helpful information? Maya's subdivision surfaces are kind of icky, any reason you're not just using Smooth Mesh preview/convert for this barrel? On second glance, your polygons look rounded anyway, is it already a sub-d shape, or are you actively in smooth preview?