VRAY material fails to show in Unreal

First of, the workflow is a bit weird:

  1. When I saved the .UDATASMITH file into my Unreal project folder, the Unreal Editor popped up a question about importing 8 files (although I’ve only saved 1), and I said yes.
  2. It seems when that happened, it built a number of textures in a Textures folder, but did nothing else (8 textures were created, actually).
  3. When I clicked the Import Datasmith button to import my .UDATASMITH file, geometry and materials were created, but no materials showed up.

When I edit a material in Unreal, it looks like this (note the ERROR and that it appears as the default checkerboard):

And when I edit the same material in Max, it looks like this:

It’s a super simple material, so I don’t understand where all the multitudes of Add nodes come from.