OK, I tried again.
I uninstalled OD Media Console, reinstalled it. Changed Adobe DE password to match PE registration pwd.
All the library books already downloaded disappeared. I downloaded another book. But, same problem. OD console can open it.
But tapping reader and opening the file fails with the error message "[book name] could not be opened". I also tried adding it to the Library first, but got the message "There was an error encountered in adding the document to the library".

I think the DRM is preventing it. Huh!