Unable to install languages, including default en-GB on Node.js

Getting these errors when trying to add languages, even the default language. Currently in the Control Panel, under Languages it shows I have zero installed.

Added the languages to the tiddlywiki.info config as per docs.

{
    "description": "Basic client-server edition",
    "plugins": [
        "tiddlywiki/tiddlyweb",
        "tiddlywiki/filesystem",
        "tiddlywiki/highlight",
        "tiddlywiki/markdown",
        "tiddlywiki/geospatial"
    ],
    "themes": [
        "tiddlywiki/vanilla",
        "tiddlywiki/snowwhite"
    ],
    "languages": [
        "en-GB",
        "en-EN"
    ],
...

returns:

Warning: Cannot find plugin 'en-GB'
Warning: Cannot find plugin 'en-EN'

What am I missing ?

en-GB is the default language and will not be shown as plugin, because it is part of the $:/core plugin.

How did you create and start your wiki? Please post the commands you used.