The Codestyling Localization plug in is apparently not yet ready for WordPress 4.0, based on : https://ww.wp.xz.cn/support/topic/when-the-plugin-will-work-wis-wp-4?replies=1.
I am looking for a workaround, perhaps http://poedit.net/ ?
My site uses WordPress 4.0, the latest update of the TwentyTen theme, and Polylang 1.5.5. Everything is translated fine, except for some of the automatic texts generated with posts and comments.
For example, if you go to http://www.savoiretcroire.ca/articles-disponibles-en-francais/ it uses English “posted on… by… ” instead of French…
In my case there is not a lot of text that needs to be translated with such a tool… So what would be the best tool to use?
I finally understood what the problem was my using TwentyTen English version for a basis, without the Spanish and French .mo files.
I found the Spanish Language .mo at http://www.ngeeks.com/traduccion-al-espanol-del-tema-twenty-ten-wordpress-3-0/ and French mof files at: http://www.dominiqueleweb.com/creation-de-site-blog/wordpress/2010-09-wordpress-3-traduction-twenty-ten-1-1.
All I had to do was then copy both .mo files to TwentyTen Language directory, naming the files exactly as they are named within my Polilang trilingual configuration setting.
Everything began working fine, so far. All labels were translated as they should be in all of my site language : http://www.savoiretcroire.ca
Hoping this might be useful to others as well.