[Solved] Failed to load plugin url: wp-includes/js/tinymce/langs/fr.js
This is a result of hard caching and JS file minifying. Please make sure the forum page is excluded from all your caching and JS/CSS optimizing plugins. Then delete your browser cache.
I'd also recommend you disable all plugins, especially the cache and optimizer plugins, and test it again. This is a plugin conflict, for sure, and you should find the problem maker yourself.
It's ok for me... thanks a lot sir