robots.txt 404 error when logged out

Aloha! I get a 404 error when I’m logged out of admin. Works fine when logged in. Search engines also getting 404 error and now my site isn’t being indexed (I assume it’s because of this?).

Been almost a week now trying to figure out why I’m not being indexed, and all indications after exhaustive research seems to point to my robots.txt file.

Any help is greatly appreciated.