Visual Editor Tab not working

Hi,
After updating to the latest version we are having problems with the Visual Editor Tab in the Post of Page window. The Text Editor Tab is selecting and the Visual tab isn’t doing anything.
I uploaded all files in the root (except wp-config.php and wp-content). No succes. In the inspector console i get two errors:
Failed to load resource: the server responded with a status of 403 (Forbidden)
post.php:2195 Uncaught ReferenceError: tinymce is not defined
But nothing had changed on the server?
I can’t work in Visual editing mode anymore. But other users need to because the don’t understand html. How can i solve this issue?