By the way, permanently decrypting the file, then encrypting it again (with the same password) on my Mac worked. And now the note opens as usual on Mac, web, and android.
Which doesn't change the fact that this just shouldn't happen. What if it didn't open anywhere? What if the only device I had was Android, and getting the information from the note was crucial.
This is not cool Evernote, and it makes me wonder if I can depend on this tech going forward.