I would suggest inspecting your wp-includes directory, specifically the .htaccess file.
I had a similar problem as well. Visual and Text buttons weren’t clickable and the text was showing up as white.
After looking into it, I realized the problem. Yesterday I used Sucuri’s hardening function to restrict direct access to php files in wp-includes. By doing this, it modified the .htaccess file inside wp-includes and added the following:
<FilesMatch “\.(?i:php)$”>
<IfModule !mod_authz_core.c>
Order allow,deny
Deny from all
</IfModule>
<IfModule mod_authz_core.c>
Require all denied
</IfModule>
</FilesMatch>
<Files wp-tinymce.php>
Allow from all
</Files>
<Files ms-files.php>
Allow from all
</Files>
After removing this code my text editor was working fine. Hope this helps.