Symptoms
The Knowledge Management Internationalization plugin does not appear to be working properly after following the instructions in the doc pages:
https://docs.servicenow.com/bundle/madrid-servicenow-platform/page/product/knowledge-management/concept/c_I18NKMInternational.html
When opening an existing article, selecting the "New" option under translated versions, it is required to choose a knowledge base, the language to translate to, and to type in a short description. After clicking on "Submit" however, the translated version shows blank.
Resolution
Even after installing the required language plugin, the Knowledge application does not automatically translate the articles to the language which is given in the language field. Users need to translate them manually.
For example, to translate an English article to Spanish, a new article needs to be written in Spanish, setting its language accordingly, and added to the original article translations.