Pipe not closing

Hi all,

I have this hexagrid projected onto a surface I want to pipe, every one of the hexagons (or trimmed hexagons on the edges, such as the one in the picture) are closed curves (I suppose). When I try to pipe them they appear to forget to end itself and continues to pipe into thin air.

I want it to close itself just like the curve I am piping.

Why does this happen and how can I fix it?

Thanks very much,

Ching