erodriguezp make sure your webserver is able to write to the storage/locale folder and that your server isn't out of disk space.
Are you running in debug mode? Flarum shouldn't attempt to generate locale files during regular requests.
A PHP Warning will not prevent Flarum from running. You should disable PHP Warning output in the php.ini config (display_errors directive) though to prevent the EmitterException that then prevents the page from showing up.
