If your sites use a visual pages 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 have internal caching functionality and a function to purge their internal cache. Please ask the developer of your page builder if you are unsure 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.