Spatial Join 3D point datasets: Ecological Marine Units (EMUs)

I have a global set of sampling points (N = 500+) that I would like to attribute with the Ecological Marine Unit (EMU) classifications near which they fall. The EMU dataset and my sampling dataset are both points datasets, and 3D, i.e. they have XYZ data. How can I extract the EMU attributes to my sampling dataset?

I am working with the EMUGlobal package (downloaded from ESRI) in ArcGIS Pro, and ran a Spatial Join of EMU dataset to my sample point dataset. Because they are both point datasets, and 3D, I ran Match Option "Intersect 3D" with a search radius (I experimented with various radii). Every time I run the Join, all the joined fields are "0," even when my search radius is extremely large and would certainly encompass nearby EMU points.

I would like to know how to attribute my 3D point dataset with attributes from this other 3D point dataset.