If your sites use a visual page builder plugin like DIVI, Elementor, Oxygen, or similar and the visual editor does not load or work properly please activate first the permalinks on the staging site.
Also, delete all WordPress caches on your site if you use a separate caching plugin.
Many page builders also come with internal caching functionality and offer a function to purge their internal cache as well. Please ask the developer of your page builder if you are not sure how to do this.
Usually this fixes those page builder issues.
If your page builder plugin still does not open, please get in contact with us.