I have dropped in the properly formatted (I ran it through a verifier) XLIFF dictionary file with translations.
i18n is on in settings.yml
I have verified that my culture code is set differently then the default culture, and the same as the culture code in the filename of the messages.(culture).xml
Yet the site just loads in English.
I don't even know how to debug this.
I started putting var_dumps in symfony functions as I walked the path into symfony from the __() helper functions, but nothing.