Numbers 3.2 won't open file

I've seen related posts to this, but no solution has worked for me. I'm running Numbers 3.2 (and only 3.2). No older version is installed on my machine. The file I am trying to open has never been stored in iCloud. The error message simply reads: "filename.numbers" can't be opened.

I can open the file in preview. What the ****? Do I have to go back to using Microsoft Office? This is disappointing.