A few days ago I asked this question (Adding rich text editor to my plugin).

Today I started building a new website in wich I copied the code of my plugin used at the website from my previous question.

And I was surprised when I saw that the exact same code that was bugging at my previous website is working perfectly fine in the new website I'm building.

For the people who did not read my previous topic: At my another website WP_editor is opening in the 'Plain text' field. I can type there and use options like Bold, Italic etc. As soon I switch to the Visual tab, my text is deleted just as all the options. All I see is a blanco tab wich cannot be edited.

The code I'm using to display the editor:

 add_action( 'edit_page_form', 'content' );
                wp_editor(
                    "Sample",
                    'content',
                    array( 'textarea_name' => 'content' )
                );

Is someone familiar with this problem or someone who knows a solutions for this? Thanks in advance!

EDIT: Getting the following errors:

GET http://www.domain.com/wp-includes/js/tinymce/langs/nl.js?ver=358-23224 404 (Not Found) wp-tinymce.php:1
Failed to load: http://www.domain.com/wp-includes/js/tinymce/langs/nl.js wp-tinymce.php:1
GET http://www.domain.com/wp-includes/js/tinymce/themes/advanced/langs/nl.js?ver=358-23224 404 (Not Found) wp-tinymce.php:1
Failed to load: http://www.domain.com/wp-includes/js/tinymce/themes/advanced/langs/nl.js