I’m experiencing the same thing on over 30 websites that I manage. This has become a very serious issue. WP 3.9 has made many very popular plugins basically useless because the WYSIWYG editor no longer functions.
What “Advanced Editor” are you referring to? Is this a plugin? Only there’s just the Text and Visual editors in WordPress by default.
I am referring to the Visual editor which I thought was also referred to as the “Advanced Editor”.
Ah! It’s just called the Visual or WYSIWYG editor. “Advanced” suggests a 3rd party plugin editor. Have you tried:
– deactivating all plugins to see if this resolves the problem. If this works, re-activate the plugins one by one until you find the problematic plugin(s).
– switching to the default theme to rule out any theme-specific problems.
– resetting the plugins folder by FTP or PhpMyAdmin. Sometimes, an apparently inactive plugin can still cause problems.
– re-uploading all files & folders – except the wp-content folder and wp-config.php & root .htaccess files – from a fresh download of WordPress. Make sure that you delete the old copies of files & folder before uploading the new ones.
