Ive recently had this problem and wondering how to fix, but mine got uploading files of JS in TinyMCE plugin, that helped me to view the Editor buttons. In my case it was easily fixed, however there are few more types but you should know how to fix the white text and missing buttons issue in WordPress visual editor.
Sometimes we might blindly click Toggle Toolbar, so try once more time whether that is working or not n most cases it gets corrupted or for CACHE issues, so I might suggest you to check these things.
See Before applying the editor shows like this
Clear the Browser Cache
I would suggest you to simply clear the browser cache or use some other browser or else use another laptop, desktop or android to see whether the problem persists within browser or in the server.
Replacing TinyMCE Scripts
Replace or upload the TinyMCE files again because most time we get corrupted by someone or something happens, but lets give a try and see if the problem get solved. If anything comes problem again please upload a fresh copy of WordPress and all plugins separately because of hackers that may get corrupted without being aware of us.
You have to just upload first TinyMCE files to the /wp-includes/js/tinymce/ folder on your server by using FTP and at that please overwrite the files.
Fix with wp-config
If the above steps all failed, then try with this WordPress config file that will perform an account to restore the TinyMCE editor. Just place this code at the top of your WordPress config file that is wp-config.php, which is in the root directory of your WordPress installation.
Make sure to place the code just after the opening tag of php.
define('CONCATENATE_SCRIPTS', false); [/code]