Snaping doesn't work on a plane

I would like to know why the snapping doesn’t work on this plane.
I tried on two computer with rhino6, neither of them can perform snap on this piece of rectangule… (fyi: it is an exploded piece from a map 3D massing)
Item.3dm (22.8 KB)

Please tell me the reason why it happen and how can I fix it! Thank you very much

Hello - this is a mesh - only the Vertex snap will work on it - to make a surface from this, use the ToNurbs command.