Here is an example of the attributeTransfer SOP working just fine.

I'm selecting a group of points, then grabbing the center of those points from a bounding object.

I'm transferring the center of one of the sides of the bounding box to another grid.

This works here, but not in my other file where the only difference is the incoming bounding object is from a more complicated scene.

I spreadsheet each incoming attributeCreate, but the transfer isn't taking.
It stays as the first input. Not sure why.

H8.1

EDIT: As always there is an alternative method. I took all the points in the bound and placed them at center using a point sop. Then deleted all but one point. Then used a copy sop to place grid at center of bound (now a single point) instead of using the attributeTransfer.