Server Response Headers
Visual Composer in ACF field is loading in iframe. Therefore, server header X-FRAME-OPTIONS plays crucial role here. Make sure it is set to “SAMEORIGIN” to allow content loading in iframe. Otherwise, you’ll see blank screen.
Conflict with theme or another plugin
Another issue could be that VC ACF field scripts conflicts with theme’s JS or JS of other plugins. Few things you can do yourself:
- Open browser console in developer tools and read errors, this may give a hint of what’s going wrong
- Try disabling other plugins, until you find the one that conflicts
- Try switching to default WP theme
In order to investigate such issues, you need to provide WP Admin and FTP access to developer.