I don't think you're supposed to attatch the elements in a patch model. I think you only need to fix the alignment of the surfaces.

I know that you can tweak the surfaces manually, by; making the 2 + 2 cv's that is on both of the opposing nurbs-surfaces, making them aligned in a line, in that way, the surface will flow perfectly from one to the other. You can draw a 1 degree line and place it near a cv and snap the two other cv's onto it.

I also know you can use the global stich and the edge-stitch tools.
But theyt may need some tweaking.

And some five corner patches may need manual tweaking anyway. Five-corner-pathces are a set of five patches, which meet at the same point. Optimally you only have a four-corner-patch, where four pathces meet. With five, the tangency may be less than acceptable, when using any alignment tools. But I'm still a newbie.

But keeping the tangency is important when makin the seams not visible.

The secret is the end-cv's which makes a line when you go from viewing cv's to viewing hulls. The hulls reflect the cv's and should be a perfect straight line (perfect tangency) from the end of a patch to the other end of the other patch.

I opened your file and got to use the stitch edge tool and for pairs of surfaces, it worked like a charm.

Hope this help a little.