Hi Takayuki,
I also use the following plugins:
-
Advanced Custom Fields
Custom Post Type UI
Relevanssi
Share Buttons by AddThis
The site is not up and running yet. I currently have everything in my local development environment. It will be great if you can give me some hint as to what may have gone wrong. But like I said, nothing was changed (both codes and configurations) and CF7 suddenly stopped working and gave me the error message I mentioned in my previous post.
Thanks a lot!