It is worth to mention in http://doc.ez.no/eZ-Publish/Technical-manual/4.6/Features/Multi-language/Managing-the-translation-languages this document, that it might be necessary to add newly added language to [RegionalSettings]SiteLanguageList[] of a siteaccess if [RegionalSettings]ShowUntranslatedObjects is disabled. Otherwise the language won't be show when translating an object.