Just ran into the same issue. In my case, the reason was simple. When you install an English-only version of WordPress, there is no
languages subdirectory under the
wp-content directory. Create it manually, and you will receive all available language list at your WP dashboard.
1. Create the target directory
By default, the "content" directory is
<wordpress folder>/wp-content. However depending on your installation it might not be that one.
To check, run
wp eval "echo WP_CONTENT_DIR;"
Once you have identified that directory, create a
languages directory in it.
2. Install languages
If Wordpress doesn't have permissions to install languages for you into that folder, you can do it yourself by placing the
.mo files in it. Restart Wordpress and it will pick them up.
3. Install languages for plugins and themes
3.1 First option: Let Wordpress download them
At this point, you got WP core translation files, but not the plugins or themes ones. To get all other translation files, go to Updates section under Dashboard, and click Check again button. At the bottom of the page you'll see a message New translations available. Click on the Update translations button, and WP will download all available translations for your plugins and themes.
3.2 Second option: place them yourself manually
As mentioned above, Wordpress must have write permissions on
languages directory, in other case you'll have to download all translation files manually. Place
.mo translation files for installed themes in
languages/themes subdirectory, and translation files for installed plugins in