Problem setting boundary for Voronoi with an extruded surface

Hello,

I have been following a tutorial on vimeo and it creates a voronoi from a divided surface which had been referenced from rhino. Now it extrudes that original surface and plug it in as the boundary for that voronoi. However, when i follow it and does the exact same thing it gives me an error. I got no clues to why this is happening, maybe it has something with the updated flatten tree component? (on the tutorial the flatten tree component was a bit different because it was on an older version but im pretty sure it is still that component i have used)

I have attached an image for this, hopefully someone could get an look at it.

Cheers,
Andy