I found that there is a problem with other plugin, The Events Calendar.
Looks like there is a compatibility issue with Yoast SEO when I try to delete The Events Calendar plugin.
In fact, I got blank page after removing The Events Calendar and Yoast SEO was activated. When I installed back The Events Calendar, everything worked fine.
Anyone can help me to solve this issue?
I had this same problem with Yoast SEO at about the same time, but I don’t even have the Events Calendar plug-in.
The Yoast SEO section of my Posts page is not visible, I can’t tag any posts, my Add Media button doesn’t work, etc. This happened to me a few days ago and I updated to the latest version of Yoast SEO and it started working again. Now I have the latest versions of WordPress (4.0) and Yoast and it’s not working.
I tried deactivating and reactivating the plug-in and that didn’t work.
Could someone help me with some suggestions for someone who doesn’t have the Events Calendar plug-in?