that’s it. I manually changed the energy column from keV to eV and it works.
Huh, OK -- I don't know why that should sometimes cause a problem, but it should be a good clue.
We should probably make sure that when Larch or XAS Viewer writes an Athena Project file that it forces energy to be in eV. And somewhat related, we were just having a discussion for Larch about adding more and better routines for reading Spec files.